The present invention relates to a method for colouring a polymeric film and to a coloured polymeric film. Furthermore, the invention relates to a master colour batch obtainable by said method, a use of said master colour batch, rigid packaging, and an injected moulded product, such as a bottle.

Plastic articles are useful for a wide variety of applications. Furthermore, the recycling of coloured plastic articles is even more important than ever before, as the volume of plastics discarded has proliferated in the last few decades. There is a great demand for more and more complex materials to satisfy the different aspects of the packaging industry.

Plastics are for example used extensively for beverage bottles, including bottles for carbonated soft drinks and other liquids. Many of the articles used in this way are coloured by various types of pigments or colorants to enhance their appearance or to protect the contents of the bottle from ultraviolet radiation.

There is a great need in the recycling industry for better methods and technologies for colouring plastics and/or removing colourants from plastics. Conventionally, a plastic material that is to be recycled is typically washed, flaked or pelletized, and then supplied to a solid-state reactor in the process of converting waste plastic into various articles. The recycling of coloured plastic material into granules leads to dark grey or black granules. One main bottleneck of these granules of recycled plastic material is that they must be compounded with virgin material to be able to provide the desired colour during further use. Often this leads to colour differences. The colour differences may be reduced by adding other colourants such as titanium dioxide. However, this impairs the physical properties and processability of the plastics, which further restricts their range of application. In particular, further recycling is made much more difficult because additional colourants are added with each cycle, and thus further impairing the physical properties of the polymer.

An objective of the present invention is to provide a method for sustainably colouring a plastic in which the abovementioned problem does not occur or at least to a lesser extent.

This objective is achieved with the method for colouring a polymeric film, wherein the method comprises the steps of:

- providing a polymeric film comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer; and

- colouring the one or more polymeric layers in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature.

It is noted that the phrase “adjacent” as used in this application is considered to be similar to “directly adjacent” and/or “contiguous with” and these phrases are used interchangeably in this application.

It is also noted that the glass transition temperature may be determined using NEN-EN-ISO 6721-11:2019 and/or ASTM E1640-18 EN 2018 and/or ASTM D6604-00 EN 2017.

Furthermore, it is noted that the glass transition temperature of the polymeric film decreases from the inside to the outside.

Furthermore, it is noted that the polymeric film may comprise one or more polymeric layers on one or both sides of the polymeric backbone layer. For example, the polymeric film may be formed from a thermoplastic material/polymer.

The method according to the invention may start with the step of providing a polymeric film comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer. Said step may than be followed by the step of colouring the one or more polymeric layers in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature.

For example, the order of their glass transition temperature may be an order starting with a high glass transition temperature to a low glass transition temperature. In other words, the glass transition temperature of the polymeric backbone layer may be higher compared to the one or more polymeric layers, wherein the glass transition temperature of the individual layers decreases in a direction extending away from the polymeric backbone layer.

The colouring of the polymeric film may be performed using a colouring agent, which may be provided to the polymeric film as a solution.

In addition, the polymeric film provided by the method according to the invention comprises a polymeric backbone layer and one or more polymeric layers, wherein the polymeric backbone layer and each of the one or more polymeric layers having a respective glass transition temperature, wherein for each pair of adjacent polymeric layers, the glass transition temperature of the polymeric layer that is closest to the polymeric backbone layer is higher than that of the other polymeric layer and lower than that of the polymeric backbone layer. Thus, each layer among the one or more polymeric layers and the polymeric backbone may have its characteristic morphology, describing the distinction between amorphous and crystalline solids.

It is noted that polymers with an amorphous morphology have their atoms held together in a loose structure, but this structure is never orderly or predictable. Therefore, amorphous solids may also refer to amorphous solids having no long-range order or chain entanglement.

Furthermore, it is noted that polymers with a crystalline morphology have their atoms held together in a rigid structure, wherein the structure may form folds and form orderly stacks of folded chains, known as lamellae. Lamellae bring long-range order to polymers.

Thus, the polymer chains of the polymeric backbone layer and/or the one or more polymeric layers are arranged increasingly more randomly throughout the material starting from the polymeric backbone layer to the outer polymeric layer, making atomic positions quasi-random. As a result of decrease in long-range order and decrease of crystallinity (getting more amorphous and less crystalline), the colouring of the different layers may be dependent on when the glass transition temperature of the effective layer is reached. In addition, the morphology of the one or more polymeric layers enables absorbing the colourant before the one or more polymeric layers reach the liquid state.

In fact, the polymeric backbone layer and/or one or more polymeric layers extending away from the polymeric backbone, reach a range of temperatures over which the material becomes less glassy and more rubber-like or vice versa. As a result, the polymeric backbone layer and/or the one or more polymeric layers do not have a melting point but have a glass transition temperature (T _g ).

Without being bond to a specific theory, it is assumed that the colourant, such as an organic aromatic colouring agent, may have the ability to migrate into the synthetic (polar) polymer material to thereby colour the synthetic (polar) polymer material. A migration of the organic aromatic colouring agent into the synthetic (polar) polymer material may also allow a migration of the organic aromatic colouring agent out of the coloured synthetic (polar) polymer material. Therefore, a decolouring of the coloured material may be possible. To enable a migration as unhindered as possible, the organic aromatic colouring agent preferably has a rather planar structure and preferably comprises at least one free rotation centre outside the planar structure. Further in case of ligands and/or remnants which may be spatially or sterically demanding, the ligands and/or remnants may be as freely movable as possible around a centre of rotation. This may give the organic aromatic colouring agent the ability to adapt its shape to the environment given by the matrix of the synthetic (polar) polymer material. Preferably, the organic aromatic colouring agent may not comprise a spiro-centre and/or the organic aromatic colouring agent may not comprise a large moiety that is rotation impaired. In this application a large moiety that is rotation impaired may mean that the molecular weight of this rotation impaired moiety is in the range of 320 g mol ¹ to 380 g mol ¹ . An advantage of the method according to the invention is that the different layers of the polymeric film may be coloured on demand. As a result, an efficient colouring process is achieved.

Furthermore, the polymeric film provided in the method according to the invention has a rigid core (backbone layer) and one or more less rigid/flexible polymeric layers arranged on the polymeric backbone layer. In particular, the one or more less rigid/flexible polymeric layers arranged on the polymeric backbone layer may be efficiently coloured due to the difference in glass transition temperature. As a result, the exposure of the polymeric backbone layer to thermal stress is limited to a minimum. Therefore, the strength of the polymeric film is preserved.

In other words, the one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein for each pair of adjacent polymeric layers, the glass transition temperature of the polymeric layer that is closest to the polymeric backbone layer is higher than that of the other polymeric layer and lower than that of the polymeric backbone layer enables to selectively colour the different layers. As a result, the polymeric film may be (semi) temporarily coloured. Furthermore, the polymeric film may be decoloured at a desired moment in time. Yet another advantage of the method according to the invention is that sustainable and/or environmentally friendly colourants may be used. As a result, the impact of the polymeric film on the environment is reduced compared to conventional polymeric films and/or plastics.

It was found that the colourants are (temporarily) incorporated in the polymer matrix of the polymeric backbone layer and/or the one or more polymeric layers. Said incorporation includes non-covalent bonds between the colourant and polymeric backbone layer and/or the one or more polymeric layers, preferably the bonding between the colourant and the polymer is a dipole-dipole interaction and/or hydrogen bonding. This enables incorporating and/or removing the colourant efficiently and effectively from the polymeric film.

Furthermore, the method according to the invention enables using colourants that may be extractable from the polymeric film. Therefore, a reusable plastic film and/or plastic is achieved.

In a preferred embodiment, decolouring may include a reductive process including a base, and an oxidative process including a peroxide. Preferably, the base is an organic base and/or the peroxide is hydrogen peroxide.

An advantage of said decolouring is that degradation of a polymer forming the polymeric layer is reduced or prevented. Therefore, the polymer may have an extended lifetime, even after multiple times of colouring and decolouring.

In a preferred embodiment according to the invention, the step of colouring comprises one or more respective colouring sub-steps, wherein each sub-step comprises colouring a single layer.

Providing one or more respective colouring sub-steps, wherein each sub-step comprises colouring a single layer, enables colouring each individual layer of the polymeric film. As a result, the amount of different colouring agents may be reduced. For example, only red, blue, and yellow may be used in order to obtain all other possible colours.

In a further preferred embodiment according to the invention, the respective colouring substeps may be performed in an order from the most inward polymeric layer relative to the polymeric backbone layer to the most outward polymeric layer relative to the polymeric backbone layer. Preferably, each colouring sub-step may be performed at a decreased temperature relative to a previous colouring sub-step.

It is noted that the polymeric backbone layer may also be coloured, preferably coloured before the one or more polymeric layers.

It was found that performing the respective colouring sub-steps in an order from the most inward polymeric layer relative to the polymeric backbone layer to the most outward polymeric layer relative to the polymeric backbone layer provides an efficiently and effectively coloured polymeric film.

In addition, colouring the polymeric film at decreasing temperatures reduces or prevents mixing of colourants in the polymeric film. This enables tuning the desired colour of the polymeric film in an efficient and effective manner.

In a further preferred embodiment according to the invention, the colouring of a polymeric layer of the one or more polymeric layers may be performed at a temperature that may be substantially equal to the glass transition temperature of said polymeric layer.

It is noted that substantially equal to the glass transition temperature means ± 15 °C of the glass transition temperature of the desired layer, preferably ± 10 °C of the glass transition temperature of the desired layer, more preferably ± 5 °C of the glass transition temperature of the desired layer.

Colouring the polymeric backbone layer and/or a polymeric layer of the one or more polymeric layers at a temperature that may be substantially equal to the glass transition temperature of said polymeric layer enables selectively colouring the different layers. As a result, a more efficient and effective colouring of a polymeric film is achieved.

In addition, it was found that colouring the polymeric backbone layer and/or a polymeric layer of the one or more polymeric layers at a temperature that may be substantially equal to the glass transition temperature of said polymeric layer reduces or even prevents agglomeration of the colourants. Furthermore, decolouring of the polymeric film may also be performed without agglomeration of the colourants.

In addition, it was found that an efficient colour master batch may be achieved.

In a further preferred embodiment according to the invention, the colouring step comprises transporting the polymeric film through one or more colouring baths. Preferably, each of the one or more colouring baths may be configured to colour a single polymeric layer. It is noted that transporting the polymeric film also relates to dipping the polymeric film in one or more colouring baths, submerging the polymeric film in one or more colouring baths, and/or contacting the polymeric film in one or more colouring baths.

Providing the polymeric film to one or more colouring baths enables colouring the polymeric backbone layer and/or a polymeric layer of the one or more polymeric layers separately with a desired (single) colourant.

In fact, it was found that providing multiple colourants to a single layer, for example the polymeric backbone layer and/or a polymeric layer of the one or more polymeric layers, reduces the equal colouring of said layer, and a colour difference appeared in said layer. Thus, the colourants were not equally distributed.

Furthermore, it was found that repeatedly colouring the different polymeric layers provides a more intense colour of the polymeric film.

In a further preferred embodiment according to the invention, the method according to the invention further comprises the step of shredding the polymeric film.

It is noted that shredding also refers to cutting, slicing, grinding, fragmenting, and the like.

The step of shredding the polymeric film may be performed after the step of colouring the one or more polymeric layers in an order of their glass transition temperature.

The step of shredding the polymeric film enables to form a colour masterbatch. As a result, granulate may be formed from the coloured polymeric film.

Shredding the polymeric film may be performed using a hitting knife or piret.

Preferably, flakes or strips of 0.15 mm to 20 mm by 0.15 mm to 20 mm by 0.15 mm to 20 mm are achieved, more preferably 0.25 mm to 20 mm by 0.25 mm to 20 mm by 0.25 mm to 20 mm are achieved, even more 0.5 mm to 20 mm by 0.5 mm to 20 mm by 0.5 mm to 20 mm are achieved, most preferably 1 mm to 20 mm by 1 mm to 20 mm by 1 mm to 20 mm are achieved.

In addition, the shredded polymeric film may be coloured additionally. As a result, a colour master batch comprising a more intense colour may be achieved.

In a further preferred embodiment according to the invention, the method according to the invention further comprises the step of forming a granulate.

The step of forming a granulate may be performed after the step of shredding the polymeric film. To form the granulate, the shredded polymeric film may be fed to an extruder and/or a worm, weir, and/or kneading element.

The granulate may be used as a colour master batch for further use. In addition, it was found that the granulate comprises a mixture of the colourants defining the desired colour of the granulate.

In a further preferred embodiment according to the invention, the method may further comprise the step of providing a colouring solution comprising a pigment. Preferably, the pigment comprises a quinone, wherein the quinone may be one or more selected from the group of 1,2- benzoquinone, 1,4-benzoquinone, 1,4-napthoquinone, 9,10-anthraquinone, l,2-dihydroxy-9, 1 Clan thraquinone.

In a preferred embodiment, the method according to the invention the colouring solution includes an emulsion, wherein the pigment is included in a hydrophobic solvent. Furthermore, said emulsion may include water.

The step of colouring the one or more polymeric layers in an order of their glass transition temperature may correspond to colouring a given polymeric layer among the one or more polymeric layers by contacting said given polymeric film with the colouring solution while said given polymeric film is at a temperature between the glass transition temperature of said given polymeric layer and the glass transition temperature of an adjacent more inward polymeric layer, and, if such layer is not present, the glass transition temperature of the polymeric backbone layer.

The colouring solution may be provided to a colouring bath, which enables to colour at least one single polymeric layer.

It was found that the pigment comprising a quinone provides an environmentally friendly, efficient, and effective colouring of the polymeric film.

In a further preferred embodiment according to the invention, the colouring solution comprising a pigment may be an aqueous solution. Preferably, the pH of the colouring solution comprising a pigment may be in the range of 2 to 12, preferably in the range of 3 to 6, more preferably in the range of 4 to 5.5, even more preferably in the range of 4 to 5.

It was found that a pH of the colouring solution comprising a pigment in the range of 2 to 12, preferably in the range of 3 to 6, more preferably in the range of 4 to 5.5, even more preferably in the range of 4 to 5, enables efficiently and effectively colouring of the polymeric film.

Alternatively, or in addition to the aqueous solution, the colouring solution may comprise acetone and/or an alcohol, such as methanol, ethanol, propanol, and the like.

It was found that a colouring solution comprising acetone and/or an alcohol increases the efficiency of the step of colouring the polymeric backbone layer and/or the one or more polymeric layers. Furthermore, it was found that a constant pH between 4 and 4.5 of the colouring solution and a concentration of at most 1 M pigment in solution provides efficient and effective colouring of the polymeric backbone layer and/or the one or more polymeric layers.

In a further preferred embodiment according to the invention, the one or more polymeric layers comprises at least two polymeric layers, preferably comprises two polymeric layers.

Preferably, the polymeric film comprises a polymeric backbone layer, a (first) polymeric layer, and a further (second) polymeric layer. Preferably, the glass transition temperature of the polymeric backbone layer is at least 10 °C higher compared to the first polymeric, wherein the first polymeric layer is at least 10 °C higher compared to the second polymeric backbone layer. In a further preferred embodiment according to the invention, the method according to the invention comprises the step of laminating the one or more polymeric layer on the polymeric backbone layer for obtaining the polymeric film.

The method according to the invention may also include laminating one or more polymeric layers on a polymeric backbone layer for obtaining said polymeric film. The, the polymeric layers are arranged on a polymeric backbone layer for obtaining said polymeric film. Said step of laminating the one or more polymeric layers on the polymeric backbone layer is performed before the step of providing a polymeric film.

The step of laminating the one or more polymeric layers on the polymeric backbone layer may start with laminating a polymeric layer comprising a glass transition temperature closest to the polymeric backbone layer on the polymeric backbone layer. Said lamination may be followed by laminating a further polymeric layer comprising a glass transition temperature second closest to the polymeric backbone layer on the first polymeric layer. As a result, a polymeric film comprising a polymeric backbone layer, first polymeric layer, and second polymeric layer is formed, wherein the polymeric backbone layer comprises a glass transition temperature which is higher than the first polymeric layer, and wherein the glass transition temperature of the first polymeric layer is higher than the glass transition temperature of the second polymeric layer.

An advantage of laminating different layer on each other is that an efficient and effective polymeric film suitable for colouring with the method according to the invention is achieved.

In an alternative embodiment, the different layers of the film may be coloured before laminating.

An advantage of colouring the different layers of the film before laminating is that the desired colour may be achieved in an efficient and effective manner. In addition, colouring the different layers separately may increase the throughput of colouring the different layers.

For example, the polymeric backbone layer may be colourless, the polymeric layer the polymeric layer that is closest to the polymeric backbone layer may be coloured blue, and the polymeric layer second closest to the polymeric backbone layer may be coloured yellow. Laminating the polymeric layer closest to the backbone layer to the backbone layer, and the second closest polymeric layer to the polymeric layer closest to the polymeric backbone layer provides a polymeric film comprising a green colour. Thus, a green master colour batch may be achieved.

In a preferred embodiment, the step of laminating is performed at a temperature below the lowest melting point of one of the polymeric layers. Preferably, the laminating is performed at a temperature in the range of 0 °C to 180 °C, preferably in the range of 5 °C to 160 °C, more preferably in the range of 5 °C to 130 °C, even more preferably in the range of 10 °C to 110 °C, most preferably in the range of 10 °C to 80 °C. It is noted that laminating of the different polymeric layers may be performed in a conventional manner.

In a further preferred embodiment according to the invention, the method according to the invention comprises the step of drying the polymeric film.

The step of drying the polymeric film may be performed between and/or after the step of colouring the one or more polymeric layers in an order of their glass transition temperature.

Drying the polymeric film enables efficiently and effectively incorporating the colourants in the different layers of the polymeric film.

In a further preferred embodiment according to the invention, the method according to the invention may comprise the step of perforating the polymeric film and/or the step of performing an additional colouring step.

The step of perforating the polymeric film is performed during and/or after the step of colouring the one or more polymeric layers in an order of their glass transition temperature and/or drying the polymeric film. In addition, the step of performing an additional colouring step may be performed, wherein said step is performed after the step of perforating the polymeric film.

The step of perforating includes providing (small) holes to the polymeric film and/or polymeric backbone layer and/or the one or more polymeric layers. It is noted that said (small) holes comprise a diameter of at most 200 micrometres, preferably at most 150 micrometres, most preferably at most 100 micrometres.

Said perforations may be provided to the polymeric film and/or polymeric backbone layer and/or the one or more polymeric layers using a laser and/or a mechanical roller/waltz/punch/die- cut. Preferably, a mechanical roller comprising spikes is used.

Perforating the polymeric film and/or polymeric backbone layer and/or the one or more polymeric layers increases the surface area of said film or polymeric layer. An advantage of perforating and/or additionally colouring the polymeric film is that a more intense and/or equally distributed coloured film is achieved. As a result, the shredded polymeric film of which a granulate may be formed may form a better coloured end-product.

In a further preferred embodiment according to the invention, the method according to the invention may comprise the step of colouring the polymeric backbone layer.

The step of colouring the polymeric backbone layer may be performed before the step of laminating the one or more polymeric layers on the polymeric backbone layer and/or is part of the step of colouring the one or more polymeric layers in an order of their glass transition temperature.

In a further preferred embodiment according to the invention, the glass transition temperature of the polymeric backbone layer may be at least 10 °C higher than the glass transition temperature of the adjacent polymeric layer, and/or wherein for each pair of adjacent polymeric layers, the glass transition temperature of the polymeric layer that may be closest to the polymeric backbone layer may be at least 10 °C higher than the glass transition temperature of the other polymeric layer.

Thus, the glass transition temperature of the polymeric backbone layer may be at least 20 °C higher than the glass transition temperature of the polymeric layer second closest to the polymeric backbone layer.

In a further preferred embodiment according to the invention, the polymeric backbone layer and the one or more polymeric layers each comprise one or more polymers independently selected from the group of polyethylene, polypropylene, polybutylene, polyisobutylene, ethylenevinylacetaat copolymer, ethene-acrylate ester copolymers, ethyl methacrylate copolymer, caprolactone polymer. Preferably, the polymer of the one or more polymers comprise low-density polyethylene more preferably linear low-density polyethylene and/or the polymer of the polymeric backbone layer may comprise high-density polyethylene.

It is noted that the caprolactone polymer is a polyester polymer derived from a caprolactone monomer, wherein the molecular weight of said polymer is between 65000 g mol ¹ and 95000 g mol ¹ , has a melting point in the range of 56 °C to 62 °C, and elongation at break between 750% and 850%. Furthermore, the melt flow index is between 2.5 g per 10 minutes to 3.5 g per 10 minutes with 2.16 kg, 1” polyvinylchloride die at 160 °C. It was found that when the polymeric backbone layer and the one or more polymeric layers each comprise one or more polymers independently selected from the group of polyethylene, polypropylene, polybutylene, polyisobutylene, ethylenevinylacetaat copolymer, ethene-acrylate ester copolymers, ethyl methacrylate copolymer, caprolactone polymer, a polymeric film is provided that may be efficiently and effectively coloured.

For example, the polymeric backbone layer may comprise polyethylene, preferably high- density polyethylene, the polymeric layer adjacent to the polymeric backbone layer may be low- density polyethylene, and the polymeric layer adjacent to the polymeric layer comprising high- density polyethylene may comprise ethyl methacrylate copolymer and/or caprolactone polymer.

In an alternative embodiment, the polymeric backbone layer and the one or more polymeric layers each comprise one or more polymers independently selected from the group of:

- polybutylene, polybutyl ethylene, poly cyclohexylethylene, polyethylene, polyisobutene, polyisobutylethylene, poly (propylene), poly(propylethylene), poly(tert-butylethylene); and/or

- polyacrylate with methyl (polymethylacrylate), ethyl (polyethylacrylate), propyl (polypropylacrylate), or butyl (polybutylacrylate); and/or

- polymethacrylate with methyl (polymethylmathacrylate), ethyl (poly ethylmethacrylate), propyl (polypropylmethacrylate), or butyl (polybutylmethacrylate); and/or

- copolymers of acrylic and methacrylic esters including, among others, such as butyl (meth)acrylate, pentyl(meth)acrylate and 2-ethylhexyl(meth)acrylate; (Meth)acrylates derived from unsaturated alcohols, preferably oleyl(meth)acrylate, 2-propynyl(meth)acrylate, ally l(meth) acrylate, vinyl(meth)acrylate; and/or

- ary l(meth) acrylates polymers, preferably benzyl(meth)acrylate polymers or phenyl(meth)acrylate polymers, the aryl radicals each being unsubstituted or up to four times substituted; and/or

- cycloalkyl(meth)acrylates polymers, preferably 3-vinylcyclohexyl(meth)acrylate polymers, bornyl (meth)acrylate polymers; and/or

- hydroxylalkyl (meth)acrylates polymers, preferably 3- hydroxypropyl (meth) acrylate polymers, 3,4- dihydroxybutyl(meth) acrylate polymers, 2-hydroxyethyl(meth)acrylate polymers, 2- hydroxypropyl(meth)acrylate polymers; and/or

- glycol di(meth)acrylates polymers, preferably 1,4-butanediol (meth) acrylate polymers; and/or

- (meth) acrylates of ether alcohols polymers, preferably tetrahydrofurfuryl (meth) acrylate polymers, vinyloxyethoxyethyl(meth)acrylate polymers; and/or

- polymers of amides and nitriles of the (meth)acrylic acid, preferably N-(3- dimethylaminopropyl)(meth)acrylamide polymers, 7V-(diethylphosphono)(meth)acrylamide polymers, l-methacryloylamido-2-methyl-2-propanol polymers; and/or

- polymers of sulfur-containing methacrylates, preferably ethylsulfinylethyl(meth)acrylate, 4-thiocyanatobutyl(meth)acrylate polymers, ethylsulfonylethyl(meth)acrylate polymers, thiocyanatomethyl(meth)acrylate polymers, methylsulfinylmethyl(meth)acrylate polymers, bis((meth)acryloyloxyethyl)sulfide polymers; and/or

- polyhydric (meth)acrylates, preferably trimethyloylpropanetri(meth)acrylate polymers; and/or

- acrylonitrile polymers; and/or

- vinyl ester polymers, preferably vinyl acetate polymers; and/or

- styrene polymers, substituted styrenes polymers with an alkyl substituent in the side chain, preferably a-methylstyrene and a-ethylstyrene, substituted styrenes polymers with an alkyl substituent on the ring, preferably vinyl toluene, and p-methylstyrene, halogenated styrene polymers, preferably monochlorostyrene polymers, dichlorostyrene polymers, tribromostyrene polymers and tetrabromostyrene polymers; and/or

- heterocyclic vinyl polymers, preferably 2-vinylpyridine polymers, 3-vinylpyridine polymers, 2-methyl-5-vinylpyridine polymers, 3-ethyl-4-vinylpyridine polymers, 2,3-dimethyl-5- vinylpyridine polymers, vinylpyrimidine polymers, vinylpiperidine polymers, 9-vinylcarbazole polymers, 3-vinylcarbazole polymers, 4-vinylcarbazole polymers, 1-vinylimidazole polymers, 2- methyl-l-vinylimidazole polymers, N-vinylpyrrolidone polymers, 2-vinylpyrrolidone polymers, N- vinylpyrrolidine polymers, 3-vinylpyrrolidine polymers, N-vinylcaprolactam polymers, N- vinylbutyrolactam polymers, vinyl oxolane polymers, vinyl furan polymers, vinyl thiophene polymers, vinylthiolane polymers, vinylthiazoles and hydrogenated vinylthiazoles polymers, vinyloxazoles and hydrogenated vinyloxazoles; and/or

- polymers of vinyl and isoprenyl ethers; and/or

- maleic acid polymers, preferably maleic anhydride polymers, methyl maleic anhydride polymers, maleimide polymers, methyl maleimide; and/or

- dienes polymers, preferably divinylbenzene polymers; and/or

- copolymers of ethylene and propylene with acrylic esters, preferably polyethylen-block-co- polymethylmethacrylat, polypropylen-block-co-polymethylmethacrylat; and/or

- aliphatic and/or aromatic polyesters, preferabl, hydroxyl-functional dendritic polyesters, polycaprolactone, polyethylenterephthalate (PET), polytrimethylenterephthalat (PTT), polybutylenterephthalat (PBT), glycolized polyglycolterephthaltat (G-PET), amorphes polyethylenterephthalat (A-PET), polyesters of terephthalic acid, polyspiro-diol-terephthalate, polypentaspiroglycol-terephthalate (PSG), polycyclohexylenedimethylene-terephthalate, polyester based copolymer including a dicarboxylic acid-derived residue including a residue derived from an aromatic dicarboxylic acid and a diol-derived residue including a residue derived from 4- (hydroxymethyl)cyclohexylmethyl-4'-(hydroxymethyl)cyclohexan e carboxylate, polyester based copolymer including a dicarboxylic acid-derived residue including a residue derived from an aromatic dicarboxylic acid and a diol-derived residue including a residue derived from 4,4- (oxybis(methylene)bis) cyclohexane methanol; and/or

- polycarbonate (PC), 2,2-bA-(4-hydroxyphenyl)-propan (bisphenol A) polycarbonate, 2,2- bA-(4-hydroxyphenyl)-butan (bisphenol B) polycarbonate, 1, l-bA(4-hydroxyphenyl)cyclohexan (bisphenol C) polycarbonate, 2,2'-methylendiphenol (bisphenol F) polycarbonate, 2,2-bis(3,5- dibrom-4-hydroxyphenyl)propan (tetrabrombisphenol A) polycarbonate und 2,2-h/.s(3,5-dimcthyl- 4-hydroxyphenyl)propan (tetramethylbisphenol A) polycarbonate, bisphenol S polycarbonate, dihydroxy diphenylsulfid polycarbonate, tetramethylbisphenol A polycarbonate, l,l-Bis(4- hydroxyphenyl)-3,3,5-trimethylcyclohexane (BPTMC) polycarbonate, l,l,l-Tris(4- hydroxyphenyl) -ethane (THPE) polycarbonate; and/or

- aliphatic polyamide (PA), preferably PA 6 based on polycaprolactam, PA 6.6 based on 6,6- hexamethylendiamin and adipic acid, PA 6.66 based on caprolactam, co-poymer of hexamethylendiamin and adipic acid, PA 66.610 based on hexamethylendiamin, copolymer of adipic acid and sebaic acid, PA 4.6, PA 10, PA 12 and PA copolymers; and/or

- polyurethane; and/or

- polar-copolymere, maleic anhydride-olefin copolymer; and/or

- polyalkylenoxide, polyalkylene block copolymer, propylenoxide-ethylenoxide copolymer, (m)ethylene acrylate-maleic anhydride copolymer; and/or - polar-terpolymere, preferably reactive terpolymers of ethylene, acrylic ester and maleic anhydride, or ethylene, methacrylic ester and maleic anhydride, or ethylene, acrylic esters and glycidyl methacrylate, or ethylene, methacrylic esters and glycidyl methacrylate, or ethylene, (meth)acrylic esters and methyl (methyl(meth)acrylate), ethyl (ethy(meth)-acrylate), propyl (propyl(meth) acrylate), or butyl (butyl(meth)acrylate), polyamide, polyester-polyamides, or butyl (butyl(meth) acrylate), polyether-polyamide copolymers; and/or

- polar polymer blends, preferably polycarbonate/polyethylenterephthalat blends (PC/PET blends), polycarbonate/polybutyleneterephthalate blends (PC/PBT blends), blends of polycyclohexylene dimethylene terephthalate copolymer, blends of poly(butylene-adipate- terephthalate); and/or

- polyacrylnitril and polyacrylnitril-copolymers, preferably poly acrylonitrile butadiene styrene (ABS), poly styrene-acrylonitrile; and/or

- polystyrene and polystyrene copolymers, preferably styrene/butadiene co-polymer (SBR), poly styrene-isoprene-styrene (SIS), poly(glycidyl methacrylate) grafted sulfonamide based polystyrene resin with tertiary amine; and/or

- polyether, preferably polyethyleneglycol, polyethyleneglycol with at least one fatty acid coupled to the polyethyleneglycol, terminating functional groups such NHj-terminated polyethers; and/or

- functionalized polyacrylamide polymers, copolymers and terpolymers, preferably poly(2- acrylamido-2-aminopropionicacid) (polyAMPA), poly(2-acrylamido-2-amino propane sulfonic acid), poly(N-isopropylacylamide (polyPNIPAM); poly (amidoamine-co-acrylic acid) copolymer, poly(N,N-dimethylacrylamide-co-sodium acrylate), poly(acrylamide-co-sodium acrylate)/poly(ethylene glycol) semi-IPN, poly(acrylamide-co-sodium 4-styrenesulfonate), poly(acrylamide-co-sodium 4-styrenesulfonate)/poly(ethylene glycol) semi-IPN, poly(acrylamide- co-sodium methacrylate), poly(acrylamide-co-sodium methacrylate)/poly(ethylene glycol) semi- IPN, and/or poly(N-isopropylacrylamide-co-acrylic acid) and poly(acrylamide-co-acrylic acid; and/or

- poly(ether sulfones)/poly(ethyleneimine) (PES/PEI), polyvinylpyrrolidone, preferably poly(N-vinyl-2-pyrrolidone), poly(N-vinyl-2-pyrrolidone-co-acrylonitrile) treated with hydroxylamine-hydrochloride; and/or

- polyvinyl alcohol; and/or

- poly(l-naphthylamine)-camphorsulphonic acid.

In a preferred embodiment, the polymeric film is not a blend, but is constructed of separate layers. An advantage of a polymeric film constructed of separate layers is that the materials of the different layers may not blend. As a result, the colourants may only incorporate in the desired layer, rather than penetrate all or a selection of the layers.

In a further preferred embodiment according to the invention, the method according to the invention comprises the step of calibrating the polymeric film, wherein the step of calibrating comprises the step of calibrating the initial colour of the polymeric film.

The step of calibrating the polymeric film may be performed before the step of colouring the one or more polymeric layers in an order of their glass transition temperature.

Calibrating may refer to calibrating the colour and/or transparency of the polymeric film.

An advantage of the step of calibrating the polymeric film is that the initial colour and/or transparency of the polymeric film may be determined before colouring. Therefore, the provided colourant may be adjusted in order to obtain the desired colour in the polymeric film and/or end/intermediate product.

In a further preferred embodiment according to the invention, the polymeric backbone layer and/or the one or more polymeric layers comprises one or more additives selected from the group of polycaprolactone diol polymer, ethylene-glycidyl methacrylate copolymer, polyethylene, polyethylene terephthalate.

It was found that the addition of an additive selected from the group of polycaprolactone diol polymer, ethylene and glycidyl methacrylate copolymer, polyethylene, polyethylene terephthalate to the polymeric backbone layer and/or the one or more polymeric layers increases the uptake of colourant in the different polymeric layers.

In a further preferred embodiment, the polymeric backbone layer and/or the one or more polymeric layers may further comprise an additional additive, wherein said additive is one or more selected from the group of a UV protection additive, a flame retardant, odour additive.

In a further preferred embodiment according to the invention, the method according to the invention comprises the step of heating the polymeric film to a temperature in the range of 110 °C to 180 °C, preferably to a temperature in the range of 120 °C to 160 °C.

In an alternative embodiment, the method according to the invention comprises heating substeps, wherein the temperature is adjusted to the glass transition temperature of the polymeric layer which needs to be coloured. For example, the heating sub-steps may comprise heating to a temperature in the range of 140 °C to 180 °C, followed by heating to a temperature in the range of 130 °C to 140 °C, and heating to a temperature in the range of 110 °C to 130 °C.

In a further preferred embodiment according to the invention, the method comprises the step of drying, wherein the polymeric film is exposed to a temperature below the lowest melting point of one of the polymeric layers. Preferably, the polymeric film may be exposed to a temperature in the range of 0 °C to 180 °C, preferably in the range of 5 °C to 160 °C, more preferably in the range of 5 °C to 130 °C, even more preferably in the range of 10 °C to 110 °C, most preferably in the range of 10 °C to 80 °C.

It is noted that the meting point of the polymeric layers may be determined using NEN-EN- ISO 3146:2021 method A and/or method B.

In a preferred embodiment the step of drying is performed after the step of colouring and/or after one or more of the colouring sub-steps.

It was found that drying the polymeric film reduces the excess of solvent attached to said polymeric film.

In a further preferred embodiment according to the invention, the method according to the invention comprises the step of cutting up a plate material and/or the step of decolouring the cut-up plate material.

It is noted that the step of decolouring the cut-up plate material may also be performed without cutting up the plate material.

The step of cutting up a plate material and/or the step of decolouring the cut-up plate material may be performed before the step of providing a polymeric film and/or the step of laminating the one or more polymeric layers on the polymeric backbone layer.

It is noted that the plate material may be made of the coloured film obtained by the method according to the invention.

Furthermore, it is noted that the polymeric backbone layer may comprise a blend of polymeric materials, wherein the material of the polymeric backbone layer may be made from (recycled/circular) plate material, wherein the plate material is made of a coloured polymeric film, obtained by the method according to the invention. Thus, the polymeric backbone layer may comprise a blend of polymers originating from all polymeric layers, including the polymeric backbone layer.

Experiments showed that the polymeric backbone layer made from (recycled/circular) plate material may be efficiently and effectively coloured and/or decoloured.

Furthermore, it is noted that plate material may refer to bottles, boxes, containers, and the like. Thus, the plate material may have different shapes.

Therefore, the step of cutting up a plate material and/or the step of decolouring the cut-up plate material enables a circular polymeric film, and thus reduces the impact on the environment.

In the context of this invention circular polymeric layer relates to the use of virgin-like polymer which may be used as a replacement of virgin (fossil based) polymers. As such, the circular polymers may have similar properties compared to virgin polymers. In other words, to obtain a circular polymer, polymeric waste, such as plate material and/or bottles, is recycled wherein the high quality of the polymer is maintained and a loss of properties if prevented. Therefore, the circular polymer may be part of (old) circular polymeric film, wherein the products made of the polymeric film may be used as source for circular polymers.

Circular or circularity refers to a system of closed loops in which raw materials, components, and products lose as little of their value as possible and are ideally re-used for 100%. In other words, the system aims at eliminating waste and continuous use of resources. Therefore, a circular polymeric film refers to a polymeric film derived from at least 80% raw materials that are waste from a similar or different application. The polymeric foam preferably has the same properties and/or had same use. Thus, after being processed to polymeric film, the circular polymer retains the mechanical properties so that it can be processed as, and is mechanically similar to, virgin polymer material.

An advantage of the circular polymer is that said polymers significantly reduce the environmental footprint of packaging material coloured by the method according to the invention. For example, packaging made of plastic and/or a polymeric film are often disposed and combusted or recycled in a downgraded manner.

In a preferred embodiment, the method according to the invention further comprises the steps of

- comminuting a thermoplastic material into coloured flakes;

- subjecting the coloured flakes to an extrusion process for producing coloured extruded material; and

- decolouring the coloured extruded material using a decolouring substance.

These steps enable to provide decolouring coloured thermoplastic material. Said steps may be performed before or after the method steps for colouring a polymeric film.

Furthermore, the method according to the invention may include the manufacturing of a colour master batch of thermoplastic granules or flakes. Said manufacturing comprises the steps of:

- decolouring coloured thermoplastic material according to the invention;

- colouring the decoloured extruded material using a colouring substance; and

- comminuting the coloured extruded material into thermoplastic granules or flakes.

In other words, the method according to the invention may include the steps to manufacture granulate and/or flakes, and/or decolour said granulate and/or flakes.

The invention also relates to a coloured polymeric film comprising:

- a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer; and a colourant, wherein the colourant is at least embedded in the one or more polymeric layers.

The coloured polymeric film provides the same or similar effects and advantages as those described for the method according to the invention.

It is noted that the polymeric backbone layer provides stiffness and rigidity to the polymeric film, wherein the one or more polymeric layers may be used to incorporate a colourant.

A further advantage of the polymeric film according to the invention is that each polymeric layer and/or polymeric backbone layer may have another colourant. As a result, a polymeric film may be achieved which may be used to form a granulate, also known as a colour master batch, in any desired colour.

In a preferred embodiment according to the invention, the polymeric film may have a thickness in the range of 50 pm to 3 mm, preferably may have a thickness in the range of 100 pm to 2 mm, more preferably may have a thickness in the range of 150 pm to 1 mm.

It was found that a polymeric film having a thickness in the range of 50 pm to 3 mm, preferably having a thickness in the range of 100 pm to 2 mm, more preferably having a thickness in the range of 150 pm to 1 mm, enables 17orming a colour master batch efficiently and effectively.

In a further preferred embodiment according to the invention, the crystallinity of the polymeric layer adjacent to the polymeric backbone is in the range of 35% to 60%, preferably in the range of 40% to 55%. Preferably, the crystallinity of the polymeric backbone layer is in the range of 60% to 90%, more preferably in the range of 60% to 75%.

In addition, the crystallinity of the polymeric layer adjacent to the polymeric layer which is adjacent to the polymeric backbone layer is in the range of 15% to 35%, preferably in the range of 25% to 35%.

It is noted that in this application, the crystallinity refers to a polymer’s degree of crystallinity and describes whether the polymer has an amorphous character or a crystalline character. The crystallinity can range from 0% (entirely amorphous) to 100% (entirely crystalline). The polymers of the coloured film according to the invention fall somewhere between those extremes.

The crystallinity of the different polymeric layers is determined by ISO 11357-1:2009.

In a further preferred embodiment according to the invention, the one or more polymeric layer each comprises an independently selected colourant comprising at least one pigment, wherein the pigment comprises a quinone, wherein the quinone may be preferably one or more selected from the group of 1,2-benzoquinone, 1,4-benzoquinone, 1,4-napthoquinone, 9,10-anthraquinone, 1 ,2-dihydroxy-9, 10-anthraquinone.

The invention also relates to a master colour batch obtainable by the method according to the invention.

The master colour batch provides the same or similar effects and advantages as those described for the method according to the invention and the coloured polymeric film according to the invention.

It was found that the master colour batch according to the invention may provide an efficient and effective material for forming desired products.

In a preferred embodiment according to the invention, the master colour batch may be a granulate.

A master colour batch as granulate may increase the manageability of the master colour batch.

The invention also relates to a use of the master colour batch according to the invention in the process of injection moulding.

The use of the master colour batch provides the same or similar effects and advantages as those described for the method according to the invention, the coloured polymeric film according to the invention, and the master colour batch according to the invention.

The invention also relates to an injected moulded product, such as a bottle, comprising the master colour batch according to the invention.

The injected moulded bottle provides the same or similar effects and advantages as those described for the method according to the invention, the coloured polymeric film according to the invention, the master colour batch according to the invention, and the use of the master colour batch according to the invention.

Furthermore, the invention also relates to a plastic object comprising the master colour batch according to the invention.

The plastic object provides the same or similar effects and advantages as those described for the method according to the invention, the coloured polymeric film according to the invention, the master colour batch according to the invention, and the use of the master colour batch according to the invention.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

- Figure 1 shows a schematic overview of a method according to the invention;

- Figure 2 shows a schematic overview of a polymeric film provided in the method according to the invention; - Figure 3 shows a schematic overview of a coloured polymeric film according to the invention;

- Figure 4 shows a schematic overview of a bottle made with the coloured polymeric film according to the invention;

- Figure 5 shows a schematic overview of an apparatus for performing said method for manufacturing and storing an uncoloured extruded material by recycling thermoplastic waste products; and

- Figure 6 shows a schematic overview of an apparatus for performing said method for manufacturing a colour master batch from an uncoloured extruded material.

Method 10 (Figure 1) for colouring a polymeric film follows a sequence of different steps.

In the illustrated embodiment method 10 may start with step 12 of providing a polymeric film comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer. Step 12 may be followed by step 14 of colouring the one or more polymeric layers in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature.

Alternatively, method 10 may start with step 16 of cutting up a plate material, wherein the plate material is made of the polymeric film according to the invention, and/or step 18 of decolouring the (cut-up) plate material. Step 16 and/or step 18 may than be followed by step 20 of laminating the one or more polymeric layers on the polymeric backbone layer.

Step 20 may be followed by step 12 of providing a polymeric film comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer.

The colour/transparency of the polymeric film provided in step 12 may optionally be calibrated in step 22 of calibrating the polymeric film. In addition to step 22, the polymeric film may be heated in step 24 of heating the polymeric film before performing step 14 of colouring the one or more polymeric layers in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature. In addition to step 14, method 10 may comprise step 26 of providing a colouring solution comprising a pigment. Furthermore, step 14 may comprise colouring sub-steps 28, 30, 32 and/or step 34 of colouring the polymeric backbone layer. Step 36 of drying the polymeric film may be performed between any one of sub-steps 28, 30, 32 and/or step 34 of colouring the polymeric backbone layer and/or after step 14.

Step 14 may optionally be followed by step 38 of perforating the polymeric film and/or step 40 of performing an additional colouring step and/or step 42 of drying the additional coloured polymeric film.

Step 14, step 38, step 40, or step 42 may be followed by step 44 of shredding the polymeric film and step 46 of forming a granulate.

In an illustrated embodiment polymeric film 50 (Figure 2) comprises polymeric backbone layer 52, first polymeric layer 54 comprising a glass transition temperature lower than polymeric backbone layer 52, and second polymeric layer 56 comprising a glass transition temperature lower than first polymeric layer 54.

In an illustrated embodiment polymeric film 60 (Figure 3) comprises polymeric backbone layer 62 which is optionally coloured, first coloured polymeric layer 64 comprising a glass transition temperature lower than polymeric backbone layer 62, and second coloured polymeric layer 66 comprising a glass transition temperature lower than first polymeric layer 64. Optionally, the polymeric backbone layer and/or the one or more coloured polymeric layers comprise different colourants.

Furthermore, polymeric film 60 may further comprise perforations 68.

In an illustrated embodiment injected moulded bottle 70 (Figure 4) comprises blow moulded polymeric film 72. Polymeric film 72 may be shredded and used to manufacture injected moulded bottle 70.

In an illustrated embodiment (Figure 5) a method for and an apparatus for performing said method for manufacturing and storing an uncoloured extruded material by recycling thermoplastic waste products is shown. Specifically, a method is shown in which:

- thermoplastic waste products A are comminuted to produce mix of flakes B by grinder 74;

- mix of flakes B is washed in a hot washer 76, resulting in a mix of clean, but wet flakes C;

- said mix C is then dried by dryer 78, resulting in a mix of clean and dry flakes D;

- mix of dried flakes D, together with an additive E, is subjected to an extruding process by extruder 80 for producing an extruded material F;

- extruded material F is decoloured by means 82 for decolouring an extruded material (and using a decolouring substance) and dried by dryer 84, for producing a decoloured extruded material G; and

- decoloured extruded material G is stored by being wound onto a spool by winding unit 86. In an illustrated embodiment (Figure 6) a method, and an apparatus for performing said method for manufacturing a colour master batch from an uncoloured extruded material is shown. Specifically, a method is shown in which:

- uncoloured extruded material H is retrieved from storage by being unwound from their spool by unwinding unit 88;

- the apparatus shown performs the optional step of laminating uncoloured extruded material H with additional layers using laminater 90;

- the apparatus shown further performs the optional step of cutting extruded material H, which was stored as a foil, into a plurality of filaments before being coloured by means 94, using cutter 92;

- uncoloured extruded material H is coloured by means 94 for colouring an extruded material (and using a colouring substance I) and dried by dryer 96, for producing coloured extruded material J; and

- coloured extruded material J is comminuted into colour master batch M by grinder 98, and, when exiting grind 98, may be received by a container 100 or any other suitable storage medium.

In a preferred embodiment, uncoloured extruded material H forms the polymeric backbone layer in a method for colouring a polymeric film. In this embodiment the aforementioned additional layers are polymeric layers.

According to a further aspect of the invention, a method for colouring a polymeric film is provided, comprising the steps of providing a polymeric film comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer, and colouring the one or more polymeric layers in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature.

According to a further aspect of the invention, also provided is a coloured polymeric film, comprising a polymeric backbone layer and one or more polymeric layers arranged on the polymeric backbone layer, each of the one or more polymeric layers having a respective glass transition temperature, wherein the one or more polymeric layers that are arranged on a same side of the polymeric backbone layer are arranged in an order of decreasing glass transition temperature starting from said same side, the glass transition temperature of each of said one or more polymeric layers being lower than that of the polymeric backbone layer, and a colourant, wherein the colourant is at least embedded in the one or more polymeric layers.

For the present disclosure, any step that includes combining two or more products (e.g. when mixing mix of flakes D with additive E before extruder 80; e.g. when adding a colouring substance I to means 94 for colouring thermoplastic extruded material), may be at least partially implemented by providing a dosing feeder, configured to provide an appropriate amount of at least one of the aforementioned two or more products that have to be combined.

In an experiment, a polymeric film comprising a poly(propylene) backbone layer, a high density polyethylene layer adjacent to both sides of the backbone layer, and a low density polyethylene layer adjacent to one side of the high density polyethylene layer. In other words, said polymeric film comprises a layer order of low density polyethylene layer, high density polyethylene layer, poly(propylene) backbone layer, high density polyethylene layer, low density polyethylene layer.

The polymeric layers were coloured in an order of their glass transition temperature starting with the polymeric layer(s) having the highest glass transition temperature. Therefore, the polymeric film was provided to a colouring bath comprising /V-(2-cthoxyphcnyl)-/V'-(4-cthylphcnyl)-cthlycnc diamide, wherein the temperature of said colouring bath was about 170 °C, followed by providing the polymeric film to a further colouring bath comprising 7V-(2-ethoxyphenyl)-A ^r -(4-ethylphenyl)- ethlyene diamide, wherein the temperature of said colouring bath was about 130 °C, and followed by providing the polymeric film to an even further colouring bath comprising 7V-(2-ethoxyphenyl)- 7V’-(4-ethylphenyl)-ethlyene diamide, wherein the temperature of said colouring bath was about 110 °C.

Each colouring step was performed for about 5 seconds.

In a further experiment the outer surface of a similar polymeric film as previously described was exposed to an aqueous dispersed colouring solution. Said aqueous dispersed colouring solution comprises 7V-(2-ethoxyphenyl)-7V’-(4-ethylphenyl)-ethlyene diamide being an organic colouring agent. The colouring agent was dispersed in water using sodium lauryl sulphate as dispersant.

The exposure to the aqueous dispersed colouring solution was performed at 170 °C.

The time of exposure of the polymeric film to the aqueous dispersed colouring solution was about 15 seconds.

It was found that the polymeric film exposed to the colouring solution at three different temperatures had a more intense colour compared to exposing the polymeric film only to 170 °C. Said observation was performed visually.

Furthermore, it was found that the majority of the colouring agent ended up in the backbone layer when the polymeric film was exposed to a colouring solution of 170 °C only. As a result, the method according to the invention enables selectively colouring the different layers of the polymeric film.

The present invention is by no means limited to the above described preferred embodiments and/or experiments thereof. The rights sought are defined by the following claims within the scope of which many modifications can be envisaged.