Polymer foil for processing by an optical laser

Abstract

A polymer foil for processing by an optical laser and comprising at least one polyolefin-based layer, wherein the at least one polyolefin-based layer further comprises a light-absorbing component selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP), and an additive (40) selected from a phthalate ester, nitrocellulose, steroid, or a combination thereof.

Description

DescriptionTitle: Polymer foil for processing by an optical laser

[0001] This application claims priority of the Luxembourg Patent Application number LU504886, filed on 9 August 2023. The entire disclosure of the Luxembourg Patent Application number LU504886 is hereby incorporated herein by reference.Field of the Invention

[0002] The invention comprises a polymer foil, a method for manufacturing of the polymer foil and a method for processing the polymer foil by an optical laser.Background of the Invention

[0003] A number of patent applications are known which teach polymer foils, methods for manufacturing of the polymer foils and methods for processing the polymer foils by an optical laser.

[0004] German Patent Application No. DE 102013113718 Al discloses a multi-layer polymer foil. The polymer foil has silver-colored pigments introduced into one or more layers of the foil and / or a metallization applied to at least one outer layer of the foil. At least one or more layers of the foil have at least one UV Absorber introduced into the layers, so that in combination with the layer thicknesses and the total thickness of the polymer foil, the entire polymer foil for UV and visible light in a wavelength range of 200 to 800 nm is less than 0.1 % permeable and for an observer as opaque, non-transparent and opaque. DE ‘718 provides no solution for transparent polymer foils which are permeable to more than 85 % of visible light. The UV light and visible radiation in a wavelength range from 200 to 800 nm is reflected to more than 20 %. This effect of reflection reduces the amount of energy that can be introduced into the foil.

[0005] German Patent Application No. DE 102020105077 Al teaches a polymer foil with additives for selective laser sintering. The polymer foil with the additives is composed of at least two components. The concentration of the polymer in the polymer foil is between 80 - 99.999 % by weight (percent by weight based on the total amount of the components) andthe concentration of additives is between 0.001 - 20 % by weight. The additives comprise metal phosphates and / or metal phosphites and / or tin oxide and / or indium-tin mixed oxides and / or lanthanum hexaborides. The selective laser sintering is conducted with laser wavelengths between 800 and 1600 nm, preferably in a range between 800 and 1100 nm, in particular for diode lasers, fiber lasers or solid-state lasers with wavelengths of, among others, 808, 940, 980, 1064 or also 1340, 1470 and 1550 nm. The polymer foil further comprises colorants and / or auxiliary materials with 0.1 to 10 % by weight (wt.%) as further components. It is noted that the auxiliary materials, such as indium tin oxide (ITO) or tin oxides, as disclosed in DE 102020105077 Al, have volume-specific costs that increase the batch price. The auxiliary materials functionalize the polymer foil, e.g., in the ability to convert electromagnetic radiation into heat. These auxiliary materials do not bind to polymer chains in the polymer foil and therefore act as defects in the polymer foil which lead to degradation of the mechanical properties of the polymer foil at concentrations of the auxiliary materials of around over 10 wt.%.

[0006] German Patent Application No. DE 102004045305 Al discloses laser-markable and / or laser-weldable polymers. The laser-markable and / or laser-weldable polymers comprise at least one boride compound as an absorber. DE 102004045305 Al discloses that the boride compound is used in low concentrations as the absorber. The boride compound shows a low inherent color in the visible spectral range (light wavelength 400 - 750 nm) at low concentrations. The boride compound only absorbs light in the infrared range. In other words, the polymer with the boride compound does not absorb light in the visible range, no color is absorbed by the polymer and so no conversion of light into heat can be achieved with the polymer. Processing the polymers of DE 102004045305 Al with laser light of 490 - 560 nm is therefore not possible.

[0007] UK Patent Application No. GB 2 286 147 A discloses a method of joining elongate hollow members formed from a substantially infra-red transparent polymeric material and having end portions of different diameters such that a first end portion of a first elongate hollow member can fit within a second end portion of a second elongate hollow member. The first end portion and the second end portion become fused and welded together by applying infra-red radiant energy to an infra-red absorptive layer situated between the firstend portion and the second end portion. The infra-red absorptive layer comprises a layer of infra-red absorptive material. The layer of infra-red absorptive material comprises a polymeric material containing an infra-red absorptive filler. The infra-red radiant energy is converted into heat by the layer of infra-red absorptive material. The infra-red absorptive material can only absorb energy in an infra-red range of wavelength.

[0008] German Patent Application No. DE 102017212099 Al discloses additive mixtures for polymers. DE 102017212099 Al further discloses laser-markable or laser-weldable polymer compositions containing the additive mixtures. The additive mixtures comprise phosphinic acid salts. The phosphinic acid salts of DE 102017212099 Al do not absorb radiation above 490 nm and as a result the polymer compositions cannot be processed with a laser light with a wavelength of 490 - 560 nm.

[0009] European Patent No. EP 2 094 497 Bl discloses a composition comprising a natural or synthetic polymer and a colorant. The colorant is present in a fluorescent form and a non- fluorescent form. The non-fluorescent form of the colorant is a pigment selected from the group consisting of quinacridone, diketopyrrolopyrrole (DPP), and the fluorescent form of the colorant is of the same chemical formula as the pigment. The natural or synthetic polymer is selected from the group of polyolefins, polyamides, polyurethanes, polyacrylates, polyacrylamides, for example.

[0010] US Patent Application No. US 2020047385 Al discloses a detectable thermoplastic food packaging film with a thermoplastic film comprising detectable particles incorporated therein. A plastic and / or plastic resin is used for manufacturing the plastic film and / or which is used as a base material for the plastic film. The plastic and / or plastic resin may be selected from the group consisting of (i) polyolefins, especially polyethylenes. The detectable particles comprise or consist of at least one magnetic iron oxide selected from the group consisting of maghemite (Fe2O3), and hematite (Fe2O3). A method for obtaining the detectable thermoplastic food packaging film is also disclosed in US 2020047385 Al. The method comprises a step of introducing and / or adding detectable particles into a molten plastic resin to produce a mixture comprising the molten plastic resin and the detectable particles and extruding the mixture comprising the molten plastic resin and the detectableparticles, so as to obtain the plastic film comprising the detectable particles incorporated therein. A step of extruding the mixture comprising the molten plastic resin and the detectable particles may be followed by and / or combined an inflation step and / or a step of orienting (stretching) the film and / or a step of maintaining a constant diameter of the extruded tube, especially performed with air, preferably pressurized air.

[0011] European Patent Application No. EP 1 852 270 Al discloses a laminate for laser marking. The laminate comprises a layer A comprising a multi-color developing laser marking polymer composition. This composition comprises a thermoplastic resin that may include olefin-based resins such as polyethylene, or polypropylene. The composition further comprises a chromatic colorant, such as a diketopyrrolopyrrole-based pigment, or a quinacridone-based pigment. The composition further comprises a black substance. Examples of the black substance may include inorganic pigments such as black iron oxide. The black iron oxide is generally an oxide of iron represented by the formula: FesCU or FeO-Fe2O3. EP 1 852 270 Al discloses a method for producing the laminate. The laminate may be produced by a co-extrusion method by feeding respective resins previously dried by an ordinary method into separate extruders, extruding the resins into a sheet therefrom through a multi-manifold die or a feed block die at a predetermined temperature, and then cooling solidifying the extruded sheet on a casting drum whose temperature is controlled to usually 0 to 80°C to form a laminated sheet.

[0012] US Patent Application No. US 20110117335 Al discloses a process for the permanent and abrasion-resistant coloured inscription and / or marking of plastics. US 20110117335 Al discloses a layer system comprising a resistant support layer, a lasersensitive energy absorber layer, a separation layer, a separate sealing layer and finally an inscription medium. The resistant support layer may be made of thermoplastics, in particular, the plastics consists of polyethylene, or polypropylene. The laser-sensitive energy absorber layer may comprise energy absorbers based on IR-absorbent colorants, such as Fe20s. The inscription medium consists of colorant, binder and optionally polymer component. The colorant may be quinacridones, or diketopyrrolo-pyrroles. The sealing layer can consist of polymers, such as nitrocellulose.

[0013] There is a need for improving mechanical properties of single- or multi polymer foil processed by an optical laser generating light at a wavelength between 490 nm and 560 nm.

[0014] There is a need for obtaining a color-neutral polymer foil.Summary of the Invention

[0015] A polymer foil for processing by an optical laser is taught in this disclosure. The polymer foil comprises at least one polyolefin-based layer. The at least one polyolefin-based layer comprises a light-absorbing component selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP). The at least one polyolefin-based layer further comprises an additive selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof.

[0016] The at least one polyolefin-based layer might originate from a polyolefin-based input material that is substantially green. The light-absorbing component selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP) is substantially red. The inventors found out that adding the light-absorbing component selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP) into the at least one polyolefin-based layer surprisingly enables obtaining a substantially white polymer foil. According to the polychromatic circle, it is expected that a substantially green coloration of a component might be reduced by the complementary color of this component, which means by a substantially red component. Further according to the polychromatic circle, it would be expected that a substantially green component, a substantially red component, and a substantially blue component would lead to a substantially white component, but not a mixing of only a substantially green component with a substantially red component.

[0017] The at least one polyolefin-based layer, such as polyethylene, does not absorb any radiation between 400 and 700 nm and therefore appears substantially transparent. The inventors found out that adding crystallites in the polyolefin-based layer causes light refraction and creates a white color impression, in order words, a substantially white polymer foil. The inventors also found out that the polymer foil being sufficiently thin, e.g. has a thickness < 540 pm, appears substantially transparent. The inventors assume that the nitrocellulose increases an absorption of light. The phthalate ester, i.e., the phthalate, acts as a plasticizer and so increases the expansion rate of polymer nodules in the amorphous phaseof the polymer foil. This reduces the energy transmitted by the light. The steroid acts as a crystallization grain that makes a transparent material more absorbent, and in fine renders the material white. The phenomena of crystallization and different refractive indices between crystalline and amorphous areas in the polymer foil lead therefore to a polymer foil that appears substantially white.

[0018] The term “phthalate ester” encompasses “phthalate,” “phthalic acid esters” or “phthalic acid salts.” The term “nitrocellulose” encompasses also “cellulose nitrate.” The inventors found surprisingly that the phthalate ester, the nitrocellulose, or the combination thereof, enables improving stretchability of the polymer foil. In other words, the phthalate ester, the nitrocellulose, or the combination of the phthalate ester and the nitrocellulose enables improving the elongation of the polymer foil without a fracture of the polyolefin- based layer by plastic deformation. A low concentration of the phthalate ester or the cellulose nitrate is, however, required. The inventors concluded that the low concentration of the phthalate ester or the cellulose nitrate has an anti-softening effect on the polymer foil. In other words, the phthalate ester and / or the cellulose nitrate enables increasing the relaxation speed of the polymer foil. The inventors assume that the aliphatic part of the phthalate ester and / or of the cellulose nitrate reduce interfacial tension between the polymer matrix of polymer chains in the polyolefin-based layer and the light-absorbing components dispersed in the polyolefin-based layer. This reduced interfacial tension improves the physical wetting of the light-absorbing component by the polymer matrix of the polyolefin-based layer and so increases the mechanical strength of the polymer foil.

[0019] The inventors conclude that a further possible effect of the phthalic acid esters and / or of the cellulose nitrates is an improved bonding of the polymer structure of the polymer foil modified by carbonization or foaming. The term “bonding” means that the phthalate ester, the nitrocellulose, or the combination thereof, are thermodynamically partially miscible with the polyolefin-based layer. The light-absorbing component has a surface that is at least physically wettable to the phthalate ester, the nitrocellulose, or the combination thereof due to polar bonds. The phthalate ester, the nitrocellulose, or the combination of the phthalate ester and the nitrocellulose act as adhesion promoters. The term “polymer structure” refers to the morphology of the polyolefin-based layer. The polymer structure encompassesamorphous areas, crystalline areas and a phase distribution of the light-absorbing component dispersed in the polyolefin-based layer. The carbonization or the foaming is caused by heating the polymer foil in an area of action at which the polymer foil is irradiated by the optical laser. The carbonization or the foaming induces color changes in the structure of the polymer foil. The carbonization leads to a black coloration and the foaming leads to a white coloration of the polymer foil, so that the carbonization and the foaming can be used for laser marking of the polymer foil. The nitrocellulose during the carbonization or the foaming degrades under heat, for example at 170 °C, before the polymer foil is damaged, so that the polymer foil retains its original strength. The phthalate ester increases the strength in carbonized areas or in foamed areas of the polymer foil due to the anti-softening effect of the phthalate ester.

[0020] The influence of the phthalate ester, i.e. the phthalic acid esters and / or the nitrocellulose, i.e. the cellulose nitrates, on absorption of light, i.e., electro-magnetic radiation, at a wavelength between 490 nm and 560 nm has to be further investigated. It is postulated that the aromatic part of the phthalic acid esters causes probably a Stokes shift, so that the polymer foil has a substantially high degree of absorption of light in the wavelength between 490 nm and 560 nm. It has been found that adding the phthalate ester, the nitrocellulose, or the combination of the phthalate ester and the nitrocellulose to the polymer foil results in an increase of the degree of absorption of light of the polymer foil, so that the polymer foil generates sufficient heat at concentrations below 0.1 wt.% when the phthalic acid ester is added to the polyolefin-based layer. This enables processing the polymer foil with the optical laser generating green laser light. It has also been found that adding the phthalate ester, the nitrocellulose, or the combination of the phthalate ester and the nitrocellulose reduced the transparency of the polymer foil, resulting in haze. Adding low concentration of the additive decreases the reduction of the transparency of the polymer foil, resulting in a higher haze value.

[0021] In one aspect, the steroid is selected from sitosterol, oestrogen, or a combination thereof. The steroid might originate from a previous application of the at least one polyolefin-based layer being in contact with the steroid.

[0022] The laser light at the wavelength between 490 nm and 560 nm can be used for processing the polymer foil. The light between 490 nm and 560 nm is perceptible as a green light by a human eye. It is known that the human eye is more sensitive to the light at this wavelength between 490 nm and 560 nm. The processing by the optical laser at the wavelength between 490 nm and 560 nm is made easier, for example, by laser guiding during laser cutting.

[0023] In one aspect, a ratio of the light-absorbing component to the additive in the polymer foil is between 1 / 5 to 5 / 1. In a further aspect, the ratio of the light-absorbing component to the phthalate ester or the cellulose nitrate in the polymer foil is between 1 / 5 to 5 / 1. This ratio enables increasing the stretchability, i.e., the strength, of the polymer foil to at least 15 % for a thickness of the polymer foil of less than 50 pm. In yet a further aspect, the ratio of the light-absorbing component to the phthalate ester in the polymer foil is between 1 / 3 to 3 / 1. This ratio enables improving yield stress values of the polymer foil to at least 25 % for a thickness of the polymer foil of less than 50 pm.

[0024] In one aspect, the light-absorbing component has a particle size distribution below 1.0 micrometres, and in a further aspect below 0.25 micrometres. The effectiveness of the degree of absorption of light of the light-absorbing component increase with their specific surface area.

[0025] A method for manufacturing of a polymer foil is further taught in this disclosure. The polymer foil comprises at least one polyolefin-based layer, the at least one polyolefin-based layer further comprising a light-absorbing component selected from iron oxide, quinacridone, or diketopyrrolopyrrole, and an additive selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof. The method comprises the steps of adding the additive into an apparatus. The method further comprising mixing a polyolefin-based input material with the light-absorbing component in the apparatus, thereby forming a melt, feeding the melt into a blown film die, expanding the melt through the blown film die, thereby obtaining the polymer foil.

[0026] A method for processing a polymer foil is disclosed. The polymer foil comprises at least one polyolefin-based layer, the at least one polyolefin-based layer further comprising a light-absorbing component selected from iron oxide, quinacridone, or diketopyrrolopyrrole, and further comprising an additive selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof. The method comprises processing the polymer foil by an optical laser generating light at a wavelength between 490 nm and 560 nm, for example between 500 nm and 540 nm, between 510 nm and 535 nm, and between 514.5 nm or of 532 nm.

[0027] The polymer foil can be laminated to a web to provide a strengthened backing. A use of the polymer foil (with or without the strengthened backing) is also disclosed, for example, as foil packaging with a perforation for separation, as foil hoods, or as bag packaging with a logo.Description of the figures

[0028] Fig. 1 shows a view of a polymer foil for processing by an optical laser.

[0029] Figs. 2A, 2B and 2C show views of a system for manufacturing the polymer foil.

[0030] Fig. 3 shows a flow chart describing a method for manufacturing the polymer foil.

[0031] Fig. 4 shows a flow chart describing a method for processing the polymer foil.

[0032] Fig. 5A shows a view of a system for extruding the polymer foil.

[0033] Fig. 5B shows a view of a system for laminating the polymer foil.Detailed description of the invention

[0034] The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspector embodiment of the invention can be combined with the feature of a different aspect or aspects and / or embodiments of the invention.

[0035] Fig. 1 shows an example of a polymer foil 10 for processing by an optical laser 200. The polymer foil 10 comprises at least one polyolefin-based layer 20. The polymer foil 10 comprises, for example, two, five, six or ten polyolefin-based layers 20. In a further example, the polyolefin-based layer 20 is located on a polymer layer 25.

[0036] The least one polyolefin-based layer 20 is, for example, high-density polyethylene (HDPE), medium-density polyethylene (MDPE), ultra-high-molecular-weight polyethylene (UHMWPE), low-density polyethylene (LDPE), such as linear low-density polyethylene (LLDPE), or polypropylene (PP).

[0037] The least one polyolefin-based layer 20 further comprises a light-absorbing component 30. The light-absorbing component 30 is selected from a semiconductor molecule with a band gap of 2.1 eV to 2.3 eV or from an organic molecule with delocalized % electron systems and chromophore functions. The organic molecule has an energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of between 2.1 and 2.3 eV. The light-absorbing component 30 is substantially homogeneously dispersed in the at least one polyolefin-based layer 20.

[0038] The concentration of the light-absorbing component 30 is below 0.1 wt.%, for example, between 0.03 wt.% and 0.06 wt.% in the polyolefin-based layer 20.

[0039] In one example, the particle size distribution of the light-absorbing component 30 is below 1.0 micrometres, and, for example, below 0.25 micrometres.

[0040] The semiconductor molecule is, for example, iron (III) oxide, i.e. ferric oxide, aluminium arsenide, silicon carbide, cadmium sulphide, or gallium phosphite.

[0041] The organic molecule is, for example, an aromatic azo compound, such as a diketopyrrolopyrrole (DPP). The DPP is, for example, an N-substituted alkyl diketopyrrolopyrrole or an N-substituted aryl diketopyrrolopyrrole. The DPP is, in a further example, methyl or butyl-3,6-Diphenyl-2,5-dihydro-pyrrolo[3,4-c] Pyrrol- 1,4-di on. The organic molecule is, in another example, a quinacridone. The quinacridone is, for example, Pigment Red 207 or Pigment Red 209. The organic molecule is, in a further example, a nitro compound, such as Pigment Red 3, Pigment Red 4, Pigment Red 104, and Pigment Red 108.

[0042] The polymer foil 10 comprises, in a further example, an additive 40 selected from a phthalate ester, nitrocellulose, or a combination thereof.

[0043] The phthalate ester is, in one example, a phthalate alkyl ester. The phthalate ester can be an ester of phthalic acid (PAE). In a further example, the phthalate ester is selected from dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl cyclohexyl phthalate (BCP), or dibutoxy ethyl phthalate (DBEP).

[0044] The polymer foil 10 comprises, in one example, the light-absorbing component 30 and the additive 40 in a ratio of the light-absorbing component 30 to the additive 40 of between 1 / 5 to 5 / 1, and, for example, between 1 / 3 to 1 / 1. In a further example, the polymer foil 10 comprises the light-absorbing component 30 and the phthalate ester in a ratio of the light-absorbing component 30 to the phthalate ester of between 1 / 3 to 3 / 1.

[0045] The polyolefin-based layer 20 is, for example, a recyclate. The recyclate has, for example, a gel speck concentration above 1000 nr2.

[0046] Fig. 2A shows a view of a system 170 for manufacturing the polymer foil 10. The system 170 includes an apparatus 70. The apparatus 70 comprises a hopper 90 for feeding a polyolefin-based input material 60, the light-absorbing component 30 and the additive 40 into the apparatus 70. The apparatus 70 comprises further a mixing element 105 for mixing the polyolefin-based input material 60, the light-absorbing component 30 and the additive 40, thereby obtaining a melt 80. The apparatus 70 further comprises heating elements 100 for heating the melt 80. The melt 80 is heated, for example, at temperatures between 100°Cto 280°C. The apparatus 70 is, for example, an extruder. In a further example, the apparatus70 is a single-screw extruder.

[0047] The system 170 further comprises a first conduit 110 for feeding the melt 80 to a blown film die 120. The feeding of the melt 80 to the blown film die 120 is conducted by applying pressure into the first conduit 110. The blown film die 120 has a circular opening 125. The system 170 comprises a second conduit 130 for supplying gas, i.e., air, into the melt 80. The supplying of the gas results in expanding the melt 80 through the blown film die 120, thereby forming a blown foil bubble 140.

[0048] The system 170 further comprises a collapsing frame 150 for collapsing the blown foil bubble 140. The system 170 comprises rollers 160, 165 for flattening the blown foil bubble 140 to the polymer foil 10.

[0049] Fig. 2B shows another view of the system 170. Fig. 2B shows that the apparatus 70 comprises a material outlet 210 for cutting the melt 80 into granules. The system 170 further comprises a water bath 220 for cooling the melt 80. The system 170 comprises an extruder 230 for plasticizing the melt 80.

[0050] Fig. 2C shows that the system 170 further comprises first rollers 240, 241 for separating the polymer foil 10 into two polymer foils 10. The two polymer foils 10 are then wound up on second rollers 250, 251.

[0051] Fig. 3 illustrates a method for manufacturing the polymer foil 10. In step S25, the polyolefin-based input material 60 and the light-absorbing component 30 are introduced into the apparatus 70 through a hopper 90. In an optional step S50, the additive 40 is added into the apparatus 70 at the same time the polyolefin-based input material 60 and the lightabsorbing component 30 are fed in step S25 through the hopper 90.

[0052] The term “additive” should not be considered as limited to components added to a substance to improve properties of the substance, and / or to preserve the substance, for example. The term “additive” might refer to an auxiliary agent. The additive 40, i.e., the auxiliary agent, might be comprised in the polyolefin-based input material 60. The additive40, i.e., the auxiliary agent, might be comprised in the polyolefin-based input material 60 as a residual element. The additive 40, i.e., the auxiliary agent, might have been added into the polyolefin-based input material 60 prior to the addition in step 25. The additive 40, i.e., the auxiliary agent, might have been mixed with a precursor material, followed by added into the polyolefin-based input material 60 prior to the addition in step 25.

[0053] In step S100, the polyolefin-based input material 60, the light-absorbing component 30, and optionally the additive 40, are mixed using the mixing element 105, thereby forming in step S120 the melt 80. A rotation of the mixing element 105 forwards the melt 80 through the apparatus 70. The mixing in step SI 00 comprises, for example, heating in step SI 10 the melt 80 using the heating elements 100. The heating in step SI 10 enables homogenising the melt 80.

[0054] In step S200, the melt 80 is fed to the blown film die 120 through the first conduit 110 by applying pressure. The applied pressure ranges between 20 bars and 250 bars.

[0055] In one example, the melt 80 is output in an output step SI 50 from the apparatus 70 through the material outlet 210 to be output into the water bath 220 to be cooled. Fig. 2B illustrates that the melt 80 is cut into granules at the material outlet 210. The melt 80 in form of granules is introduced in a melt-introduction step S170 in the extruder 230 to be plasticized, followed by a feeding step S200 of feeding the melt 80 to the blown film die 120 through the first conduit 110.

[0056] In a step S210, the melt 80 passes through the circular opening 125 of the blown film die 120. Simultaneously, the gas is injected into the melt 80 using the second conduit 130, thereby expanding in an expansion step S300 the melt 80 through the blown film die 120. The expansion step S300 results in forming in a step S310 the blown foil bubble 140.

[0057] The blown foil bubble 140 is collapsed in a collapsing step S320, followed by flattened in a flattening step S330, thereby obtaining a flattened blown foil bubble 140, i.e., which forms the polymer foil 10. In a separating step S340, the edge areas of the flattened blown foil bubble 140 (i.e., the polymer foil 10) are separated through the two first rollers240, 241 to separate the polymer foil 10 into the two polymer foils 10. The two polymer foils 10 are wound up in a winding step S350 on the two second rollers 250, 251, thereby obtaining in a step S400 the polymer foil 10. The polymer foil 10 can be further laminated onto a web 350 in a further lamination step S410.

[0058] Fig. 4 illustrates a method for processing the polymer foil 10. The method comprises providing in step S450 the polymer foil 10, followed by processing in step S500 the polymer foil 10 by an optical laser 200 generating light at a wavelength of between 490 nm and 560 nm. In one example, the optical laser 200 generates light at a wavelength between 500 nm and 540 nm. In a further example, the optical laser 200 generates light at a wavelength between 510 nm and 535 nm. In another example, the optical laser 200 generates light at a wavelength of 514.5 nm or of 532 nm.

[0059] The processing in the step S500 is, for example, marking, welding, or cutting the polymer foil 10.

[0060] In one example, the polymer foil 10 after the processing in step S500 is used as foil packaging with a perforation for separation, as foil hoods or as bag packaging with a logo.Examples of compositions of polymer foils

[0061] The compositions listed below are merely examples of suitable formulations and are not limiting of the invention (all percentages by weight):Composition 1Composition 2Composition 3Composition 4Composition 5

[0062] The examples listed below are merely examples of suitable process conditions for producing the polymer foils and are not intended to be limiting of the invention. Examples 1 to 3 elucidate different polymer foils which can be processed based on the compositions 1 to 3.Example 1

[0063] 250 kg / h of LDPE from post-consumer recyclate, 0,125 kg / h of iron (III) oxide and 0,025 kg / h of cellulose nitrate oligomer were mixed in the step 100 in an apparatus 70 to obtain a melt 80. The melt 80 was heated in the heating step 110 at a temperature of 190°C. In the step 200, the melt 80 is fed to a blown film die 120 at a pressure of 180 bars, expanded in the expansion step 300 through the blown film die 120, thereby obtaining in the step 400 a polymer foil 10 of the composition 1.Example 2

[0064] 320 kg / h of LDPE / LLDPE of used beverage cartons (UBC) recyclates, 0,12 kg / h of N-substituted aryldiketopyrrole and 0,4 kg / h of diethyl phthalate were mixed in step SI 00 in an apparatus 70 to obtain a melt 80. The melt 80 was heated in the heating step SI 10 at a temperature of 230°C. In the feeding step S300, the melt 80 is fed to an extruder 300 at a pressure of 250 bars with another melt of virgin LDPE and expanded in the expansion stepS300 through a wide-slot nozzle of the extruder 300, as shown in Fig. 5A, thereby obtaining in the step S400 a co-extruded polymer foil 310.

[0065] The co-extruded melt 80 and the virgin LPDE is extruded in the extrusion step S300 through a wide slot nozzle of the extruder 300 onto a water-cooled chill roll 320 for cooling the polymer foil 310 in a cooling step S405. The water-cooled chill roll 320 is at a temperature between 40°C and 65°C. The co-extruded polymer foil 310 is pinned against the water-cooled chill roll 320 by an air knife 330 and a vacuum box 340.

[0066] Fig. 5B illustrates the lamination step S410 of lamination of the polymer foil 310. The polymer foil 310 is laminated in the lamination step S410 by putting the polymer film 310 in contact with a web 350 made of a biaxially stretched PP through a gap between two lamination rolls 360, resulting in welding together of the polymer foil 310 with the web 350.Example 3

[0067] 200 kg / h of LDPE from post-consumer recy elate, 0,1 kg / h 5-chloro-4-methyl-2- sulfonatophenyl) diazenyl -3-hydroxynaphthalene-2-carboxylate calcium salt and 0,01 kg / h diethyl phthalate + 0,02 kg / h of cellulose nitrate oligomer were mixed in step SI 00 in an apparatus 70 to obtain a melt 80. The melt 80 was heated in the heating step SI 10 at a temperature of 270°C. In the step S200, the melt 80 is fed to a blow film die 120 at a pressure of 200 bars, expanded in the expansion step S300 through the blown film die 120, thereby obtaining in the step S400 a polymer foil 310 of the composition 3, as explained above in Example 2.

[0068] The polymer foil 310 is laminated in the lamination step S410 by putting the polymer foil 310 in contact with a web 350 made of a PET modified with glycol (PETG) and previously treated with a PU adhesive. The lamination step S410 results in welding together the polymer foil 310 with the web 350.Example 4

[0069] 250 kg / h of LDPE / LLDPE of post-consumer recyclate based on UBC, 0,016 kg / h of N-substituted aryldiketopyrrole, 0,028 kg / h diethyl phthalate and 0,008 kg / h B-sitosterol were mixed in step 100 in an apparatus 70 to obtain a melt 80. The melt 80 was heated inthe heating step SI 10 at a temperature of 190°C. In the feeding step S300, the melt 80 is fed to an extruder 300 at a pressure of 180 bars with another melt of virgin LDPE and expanded in the expansion step S300 through a wide-slot nozzle of the extruder 300, as described in Example 2, thereby obtaining in the step S400 a co-extruded polymer foil 310.

[0070] The co-extruded melt 80 and the virgin LPDE are extruded in the extrusion step S300 through a wide slot nozzle of the extruder 300 onto a water-cooled chill roll 320 for cooling the polymer foil 310 in a cooling step S405. The water-cooled chill roll 320 is at a temperature between 40°C and 65°C. The co-extruded polymer foil 310 is pinned against the water-cooled chill roll 320 by an air knife 330 and a vacuum box 340.

[0071] The polymer foil 310 is laminated in the lamination step S410 by putting the polymer foil 310 in contact with a web 350 made of a biaxially stretched PP film. The lamination step S410 results in welding together the polymer foil 310 with the web 350.Example 5

[0072] 300 kg / h of LDPE from post-consumer recyclate, 0,010 kg / h 5-chloro-4-methyl-2- sulfonatophenyl) diazenyl -3-hydroxynaphthalene-2-carboxylate calcium salt, 0,020 kg / h diethyl phthalate, 0,003 kg / h cellulose nitrate oligomer and 0,003 % B-methyl-gonane were mixed in step S100 in an apparatus 70 to obtain a melt 80. The melt 80 was heated in the heating step SI 10 at a temperature of 180°C. In the step S200, the melt 80 is fed to a blow film die 120 at a pressure of 150 bar, expanded in the expansion step S300 through the blown film die 120, thereby obtaining in the step S400 a polymer foil 310 of the composition 5, as explained above in Example 3.

[0073] The polymer foil 310 is laminated in the lamination step S410 by putting the polymer foil 310 in contact with a web 350 made of a PET modified with glycol (PETG) and previously treated with a PU adhesive. The lamination step S410 results in welding together the polymer foil 310 with the web 350.Reference numerals10 polymer foil20 polyolefin-based layer25 polymer layer30 light-absorbing component40 additive60 polyolefin-based input material70 apparatus80 melt90 hopper100 heating elements105 mixing element110 first conduit120 blown film die125 circular opening130 second conduit140 blow foil bubble150 collapsing frame160, 165 rolls170 system200 optical laser210 material outlet220 water bath230 extruder240, 241 first rollers250, 251 second rollers300 extruder310 polymer foil320 water-cooled chill roll330 air knife340 vacuum box350 web360 lamination rolls

Claims

Claims1. A polymer foil (10) for processing by an optical laser (200) and comprising at least one polyolefin-based layer (20), wherein the at least one polyolefin-based layer (20) further comprises: a light-absorbing component (30) selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP); and an additive (40) selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof.

2. The polymer foil (10) of claim 1, wherein the phthalate ester is selected from dimethyl phthalate (DMP), diethyl phthalate (DEP), butyl cyclohexyl phthalate (BCP), or dibutoxy ethyl phthalate (DBEP).

3. The polymer foil (10) of claim 1 or 2, wherein the steroid is selected from sitosterol, oestrogen, or a combination thereof.

4. The polymer foil (10) of any one of the above claims, wherein the polyolefin-based layer (20) comprises high-density polyethylene (HDPE), medium-density polyethylene (MDPE), ultra-high-molecular-weight polyethylene (UHMWPE), low- density polyethylene (LDPE), such as linear low-density polyethylene (LLDPE), or polypropylene (PP).

5. The polymer foil (10) of any one of the above claims, wherein the light-absorbing component (30) is sensitive to a light at a wavelength between 490 nm and 560 nm, preferably between 500 nm and 540 nm, preferably between 510 nm and 535 nm, more preferably of 514.5 nm or of 532 nm.

6. The polymer foil (10) of any one of the above claims, wherein the light-absorbing component (30) has a particle size distribution below 1.0 micrometres, preferably below 0.25 micrometres.

7. The polymer foil (10) of any one of the above claims, wherein the additive (40) has a particle size distribution below 250 nm, preferably below 200 nm.

8. The polymer foil (10) of any one of the above claims, wherein the light-absorbing component (30) has a concentration below 0.1 wt.% in the polyolefin-based layer, preferably between 0.03 wt.% and 0.06 wt.% in the polyolefin-based layer.

9. The polymer foil (10) of any one of the above claims, wherein the additive (40) has a concentration below 0.01 wt.% in the polyolefin-based layer.

10. The polymer foil (10) of any one of the above claims, wherein a ratio of the lightabsorbing component (30) to the additive (40) is between 1 / 5 to 5 / 1, preferably between 1 / 3 to 1 / 1.

11. The polymer foil (10) of any one of the above claims comprising between two and ten polyolefin-based layers (20), preferably between two and five polyolefin-based layers (20), more preferably between six and ten polyolefin-based layers (20).

12. A method for manufacturing a polymer foil (10), the polymer foil (10) comprising at least one polyolefin-based layer (20), the at least one polyolefin-based layer (20) further comprising a light-absorbing component (30) selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP), and an additive (40) selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof, the method comprises the steps of: adding (S50) the additive (40) into an apparatus (70), mixing (SI 00) a polyolefin-based input material (60) with the light-absorbing component (30) and with the additive (40) in the apparatus (70), thereby forming (S120) a melt (80); feeding (S200) the melt (80) into a blown film die (120); expanding (S300) the melt (80) through the blown film die (120), thereby obtaining (S400) the polymer foil (10).

13. The method of claim 12, further comprising outputting (SI 50) the melt (80) from the apparatus (70) in form of granulates, followed by the step of feeding (S200) the melt (80) in form of granulates into the blown film die (120).

14. A method for processing a polymer foil (10, 310) comprising at least one polyolefin- based layer (20), the at least one polyolefin-based layer (20) further comprising a light-absorbing component (30) selected from iron (III) oxide, quinacridone, or diketopyrrolopyrrole (DPP), and an additive (40) selected from a phthalate ester, nitrocellulose, a steroid, or a combination thereof, wherein the method comprises: processing (S500) the polymer foil (10, 310) by an optical laser (200) generating light at a wavelength between 490 nm and 560 nm, preferably between 500 nm and 540 nm, preferably between 510 nm and 535 nm, more preferably of 514,5 nm or of 532 nm.

15. The method of claim 14, wherein the processing (S500) is chosen from one of marking, welding, or cutting.

16. The method of claim 15, further comprising lamination (S410) of the polymer foil (310) with a web (350).

17. Use of the polymer foil according to any one of claims 1 to 11 processed by the method according to claim 14 to 16 as foil packaging with a perforation for separation, as foil hoods, or as bag packaging with a logo.

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