Polymer composition

Abstract

The present invention is in the field of polymer compositions containing carbon particles suitable for infrared spectroscopic analysis. The present invention relates to a polymer composition containing a polymer, carbon particles, and a laser absorbing additive wherein at least a portion of the surface of the polymer composition absorbs less infrared radiation than the bulk.

Description

[0001] The present invention belongs to the field of polymer compositions containing carbon particles suitable for infrared spectroscopy analysis. The present invention further relates to a method for producing a polymer composition, an article containing the polymer composition, the use of a laser absorption additive for increasing the infrared transparency at the surface of a polymer composition containing carbon particles, and the use of the polymer composition or the article for plastic sorting based on infrared spectroscopy.

[0002] Black polymers are typically filled with carbon black pigments. For recycling purposes, it is necessary to determine the type of polymer. This is typically achieved by infrared spectroscopy. However, carbon black strongly absorbs infrared radiation, which hinders the determination of the polymer type. Other black pigments with lower infrared absorbance have been proposed.

[0003] JP 2006249411 A discloses a black pigment that is reflective in the infrared spectral range, thus allowing the sorting of plastics via infrared spectroscopy. However, carbon particles, especially carbon black, have excellent light stability, an antistatic effect, and are easily obtained in large quantities at low cost.

[0004] Accordingly, there is a desire for a polymer composition containing carbon particles that can be detected by infrared radiation to allow sorting for recycling purposes. This object is achieved by the present invention.

[0005] In one aspect, the present invention relates to a polymer composition comprising

[0006] - a polymer,

[0007] - carbon particles, and

[0008] - a laser absorption additive,

[0009] wherein at least a portion of the surface of the polymer composition absorbs less infrared radiation than the bulk.

[0010] In another aspect, the present invention relates to an article containing the polymer composition according to the present invention.

[0011] In another aspect, the present invention relates to a method for reducing the infrared absorbance at the surface of a polymer composition containing carbon particles, the method comprising

[0012] a. providing a polymer composition containing a polymer, carbon particles, and a laser absorption additive, and

[0013] b. exposing at least a portion of the polymer composition to laser radiation.

[0014] In another aspect, the present invention relates to the use of a laser absorption additive for reducing the infrared absorbance at the surface of a polymer composition containing carbon particles.

[0015] In another aspect, the present invention relates to a polymer composition comprising

[0016] - a polymer,

[0017] - carbon particles, and

[0018] - a laser absorption additive,

[0019] wherein at least a portion of the surface of the polymer composition has been exposed to laser radiation.

[0020] In another aspect, the present invention relates to the use of the polymer composition according to the present invention or an article according to the present invention for plastic sorting based on infrared spectroscopy.

[0021] The polymer composition contains a polymer. The polymer may be an organic polymer. The polymer may have a molecular weight of 10 3 to 10 7 g / mol, preferably 10 4 to 10 6 g / mol. The polymers include polyamide (PA), polyurethane (PU), low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polystyrene (PS), acrylonitrile - butadiene - styrene (ABS), styrene - acrylonitrile (SAN), acrylate - styrene - acrylonitrile (ASA), polytetrafluoroethylene (Teflon), thermoplastic polyurethane (TPU), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), polybutadiene (BR, PBD), poly(cis - 1,4 - isoprene), poly(trans - 1,4 - isoprene), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly(butylene adipate - terephthalate) (PBAT), polyester (PES), polyethersulfone (PESU), polyhydroxyalkanoate (PHA), poly - 3 - hydroxybutyrate (P3HB), poly - 4 - hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polylactic acid (PLA), polysulfone (PSU), polyphenylsulfone (PPSU), and their copolymers and mixtures.

[0022] Particularly preferred polymer compositions may be selected from compositions comprising at least one polymer selected from the following: PA4, PA 5, PA 6, PA 7, PA 8, PA 9, PA 10, PA 11, PA 12, PA 46, PA 66, PA 666, PA 69, PA 610, PA 612, PA 96, PA 99, PA 910, PA 912, PA 1212, PA 6.T, PA 9.T, PA 8.T, PA 10.T, PA 12.T, PA 6.1, PA 8.1, PA 9.I, PA 10.1, PA 12.1, PA 6.T / 6, PA 6.T / 10, PA 6.T / 12, PA 6.T / 6.I, PA 6.T / 8.T, PA 6.T / 9.T, PA 6.T / 10T, PA 6.T / 12.T, PA 12.T / 6.T, PA 6.T / 6.I / 6, PA6.T / 6.I / 12, PA 6.T / 6.1 / 6.10, PA 6.T / 6.1 / 6.12, PA 6.T / 6.6, PA 6.T / 6.10, PA 6.T / 6.12, PA 10.T / 6, PA 10.T / 11, PA 10.T / 12, PA 8.T / 6.T, PA 8.T / 66, PA 8.T / 8.I, PA 8.T / 8.6, PA 8.T / 6.I, PA 10.T / 6.T, PA 10.T / 6.6, PA 10.T / 10.I, PA 10T / 10.I / 6.T, PA 10.T / 6.I, PA 4.T / 4.I / 46, PA 4.T / 4.I / 6.6, PA 5.T / 5.I, PA 5.T / 5.I / 5.6, PA 5.T / 5.I / 6.6, PA6.T / 6.I / 6.6, PA MXDA.6, PA IPDA.I, PA IPDA.T, PA MACM.I, PA MACM.T, PA PACM.I, PAPACM.T, PA MXDA.I, PA MXDA.T, PA 6.T / IPDA.T, PA 6.T / MACM.T, PA 6.T / PACM.T, PA 6.T / MXDA.T, PA 6.T / 6.1 / 8.T / 8.1, PA 6.T / 6.I / 10.T / 10.I, PA 6.T / 6.I / IPDA.T / IPDA.I, PA6.T / 6.I / MXDA.T / MXDA.I, PA 6.T / 6.I / MACM.T / MACM.I, PA 6.T / 6.I / PACM.T / PACM.I, PA6.T / 10.T / IPDA.T, PA 6.T / 12.T / IPDA.T, PA 6.T / 10.T / PACM.T, PA 6.T / 12.T / PACM.T, PA10.T / IPDA.T, PA 12.T / IPDA.T, and their copolymers and mixtures; preferably, PA 6 and PA 66, and their copolymers and mixtures.

[0023] The polymer composition contains carbon particles. The carbon particles preferably contain at least 90% by weight, preferably at least 96% by weight, especially at least 99% by weight of carbon. The carbon particles can have a particle size of 10 to 500 nm, preferably 15 to 300 nm. The particle size can refer to the weight-average particle size, which is determined, for example, by light scattering. The carbon particles can be individual particles or aggregates of particles or a mixture of both. The carbon particles can have various shapes, such as spherical, rod-shaped, or flake-shaped. The carbon particles can contain amorphous carbon, polycrystalline carbon, subcrystalline carbon (such as carbon black), and / or crystalline carbon (such as graphite, carbon nanotubes, or graphene). The polymer composition preferably contains 0.01% to 10% by weight, more preferably 0.03% to 1% by weight, especially 0.05% to 0.5% by weight, such as 0.1% to 0.2% by weight of carbon particles.

[0024] Preferably, the carbon particles contain carbon black. Carbon black can be produced by a variety of different processes, such as the furnace black process, the channel black process, the gas black process, the acetylene black process, or the lamp black process. To increase the dispersibility of carbon black in the polymer, the carbon black can be surface-modified, for example, by surface oxidation or by using a surfactant.

[0025] The polymer composition contains a laser absorption additive. The laser absorption additive can be any compound or composition capable of absorbing laser light. The laser absorption additive can be any compound or composition capable of absorbing laser light other than the carbon particles. Laser absorption additives are widely used in polymer compositions for marking plastic parts by using laser instead of paint, or for laser welding of plastic parts.

[0026] The laser absorption additive can be molecularly dispersed in the polymer, or it can be in the form of particles dispersed in the polymer, preferably in the form of particles dispersed in the polymer. The laser absorption additive in the form of particles can have a particle size of 0.1 to 100 µm, preferably 0.5 to 60 µm, especially 1 to 15 µm. The particle size can refer to the weight-average particle size, which is determined, for example, by light scattering. The laser absorption additive can contain an organic dye, such as the rylene dye disclosed in WO 2005 / 102 672 A1. Preferably, the laser absorption additive is in the form of particles dispersed in the polymer separately from the carbon particles. Thus, preferably, the laser absorption additive particles and the carbon particles are separately dispersed in the polymer, so that the laser absorption additive particles do not come into contact with the carbon particles.

[0027] The laser absorption additive can contain a metal or a metalloid, preferably a metal or a metal salt, such as an oxide, a sulfide, a selenide, a nitride, a phosphide, an arsenide or an antimonide. The laser absorption additive can contain a dopant, especially a heavy metal, especially a transition metal (such as niobium) or a rare earth metal. The laser absorption additive can be organic or inorganic, preferably inorganic. The laser absorption additive can contain a dopant in an amount of 0.05% to 15% by weight, preferably 0.1% to 10% by weight, especially 0.3% to 5% by weight.

[0028] The laser absorption additive can contain two phases, such as a core-shell structure. The core can contain a silicate material such as natural or synthetic mica, talc or sericite, undoped or doped titanium dioxide, alumina, silica, carbon, graphite, iron oxide, barium sulfate or pearlescent pigments. The shell can contain a laser absorption compound, such as (Sn,Sb)-oxide, Sb2O3 or Fe3O4. The weight ratio of the shell to the core of the pigment is in the range of 50:50 to 95:5 with respect to the weight of the entire core-shell particle. Examples of laser absorption additives containing two phases are (Sn,Sb)-oxide supported on mica or TiO2, Sb2O3 supported on polyethylene, or Fe3O4 supported on mica. Some laser absorption additives are commercially available from Merck KGaA under the trademark Iriotec®. Examples of synthetic core-shell particles are disclosed in WO 2017 / 016 645 A1 or WO 2018 / 095834 A1.

[0029] The polymer composition preferably contains 0.001% to 20% by weight, preferably 0.01% to 10% by weight, especially 0.05% to 3% by weight of the laser absorption additive.

[0030] The polymer composition can contain other components, such as fillers, and other additives, such as flame retardants, antioxidants, light stabilizers, processing aids or inorganic fillers.

[0031] Preferably, the polymer composition contains

[0032] 80% to 99.98% by weight of a polymer,

[0033] 0.01% to 10% by weight of carbon particles, and

[0034] 0.01% to 10% by weight of the laser absorption additive.

[0035] The polymer, carbon particles, and laser absorption additive can be combined in various ways, such as by blending, via a masterbatch, via a paste, or by direct addition during a shaping process step (direct coloring). The resulting mixture can be shaped into an article by molding, extrusion, or sintering. The article can contain, consist essentially of, or consist of the polymer composition. Examples of articles are consumables such as bottles, cups, syringes, bags; or structural parts such as furniture like chairs, vehicle parts like bumpers, electrical appliances like hair dryer housings or keyboards, building materials like water barrier foils or insulating foams, agricultural or horticultural parts like flower pots, toys like plastic dolls.

[0036] The surface of the polymer composition can refer to the outer layer of the polymer composition that typically faces the surrounding air. The remainder of the polymer composition can be referred to as the body and is thus typically the main part of the polymer composition covered by the surface. The surface can have a thickness of 1 µm to 5 mm, preferably 10 µm to 1 mm, for example 20 µm to 100 µm. For example, the surface of the polymer can be an outer layer with a polymer composition thickness of 20 µm, and the body of the polymer composition can be the remainder of the polymer composition.

[0037] At least a part of the surface of the polymer composition has a low absorbency for infrared radiation. This means that the entire surface of the polymer composition or only a part of the surface of the polymer composition has a low absorbency for infrared radiation. The size of this part can be set such that infrared spectroscopic analysis can be performed at this part. This can be achieved by a small area (for example, an area of 1 × 1 cm). An article containing the polymer composition can contain a label that indicates the part of the surface of the polymer composition having a reduced absorbency for infrared radiation. The part of the surface of the polymer composition having a reduced absorbency can be part of the label or can be close to the label. The label can contain product information about the article, especially information related to the recycling of the polymer composition, such as the polymer, additives, producer, or production date of the article.

[0038] The infrared radiation can have a wavelength of 760 nm to 1000 µm. The infrared radiation includes near-infrared radiation with a wavelength of 760 nm to 3 µm, mid-infrared radiation with a wavelength of 3 µm to 15 µm, and far-infrared radiation with a wavelength of 15 µm to 1000 µm. Preferably, the infrared radiation refers to near-infrared radiation, especially near-infrared radiation with a wavelength of 1.5 to 2.5 µm.

[0039] Absorbing less infrared radiation can mean that the absorbance at the surface is lower for at least one wavelength in the infrared region compared to the bulk of the polymer composition. Thus, the infrared radiation can be transmitted, diffracted, or reflected with a reduced degree of absorption. Preferably, the absorbance of at least a portion of the surface for infrared radiation is less than 50% of the absorbance of the bulk for infrared radiation, more preferably less than 30% of the absorbance of the bulk for infrared radiation, and especially less than 20% of the absorbance of the bulk for infrared radiation. The absorbance of the surface for infrared radiation is preferably low enough such that the absorption bands of the polymer can be used for detecting the polymer by infrared spectroscopy. Since carbon particles have a high absorbance for infrared radiation, their absorption can be reduced.

[0040] The reduction in infrared radiation absorption can be achieved by exposing a composition containing a polymer, carbon particles, and a laser absorption additive to laser radiation. It has surprisingly been found that the reduction of infrared radiation absorption by using laser radiation is achieved only in the presence of a laser absorption additive. This effect has not been observed for polymers containing only carbon particles, which tend to burn and form bubbles at the surface, whereas this is not the case in the presence of a laser absorption additive.

[0041] Laser radiation of various wavelengths can be used, for example, in the range from 100 nm to 32 µm, preferably in the range from 355 nm to 10.9 µm, and most preferably in the range from 800 nm to 1200 nm. Examples of suitable lasers are CO2 lasers (about 10.6 µm), Nd:YAG lasers (about 1064 nm), YVQ4 lasers (about 1064 nm), fiber lasers (about 1062 nm), green lasers (532 nm), UV lasers (355 nm), semiconductor diode lasers (405 - 3330 nm), excimer lasers (such as F2 excimer lasers (157 nm), ArF excimer lasers (193 nm), KrCI excimer lasers (222 nm), KrF excimer lasers (248 nm), XeCI excimer lasers (308 nm), and XeF excimer lasers (351 nm)).

[0042] The polymer composition can be exposed to laser radiation for various amounts of time, depending on the desired thickness of the surface layer with reduced absorbance for infrared radiation and the desired degree of reduction in absorbance for infrared radiation. Preferably, the polymer composition is exposed to laser radiation for 1 µs to 10 ms, more preferably 5 µs to 1 ms, and especially 10 to 100 µs. The power of the laser can also depend on the desired thickness of the surface layer with reduced absorbance for infrared radiation and the desired degree of reduction in absorbance for infrared radiation. Preferably, the laser power / surface area is 1 to 500 kW / mm2 , more preferably 3 to 100 kW / mm 2 , particularly 5 to 30 kW / mm 2 . The laser radiation can be pulsed, for example, having a pulse frequency of 10 Hz to 1 MHz, preferably 1 kHz to 500 kHz, particularly 10 kHz to 200 kHz.

[0043] Therefore, the laser absorption additive can be used to reduce the infrared absorbance at the surface of the polymer composition containing carbon particles. The laser absorption additive can be used to enable infrared spectroscopic analysis of the polymer composition containing carbon particles. The laser absorption additive can be used to achieve plastic sorting based on infrared spectroscopy. The laser absorption additive can be used to achieve the recycling of the polymer composition. Articles containing the polymer composition of the present invention can be subjected to infrared spectroscopic analysis at a surface with reduced infrared absorbance. In this way, the chemical properties or the type of the polymer in the polymer composition can be detected, such as PA and PP. This allows sorting of different polymer-containing articles according to the type of polymer in the polymer composition. Without such sorting, a polymer mixture of poor quality is obtained, and thus meaningful recycling is not possible.

[0044] Examples

[0045] A polyamide 6 containing 0.4% of Fe3O4 loaded on mica (< 15 µm) and 0.1% of carbon black powder (P.BK.7) was molded into a plate. The plate was irradiated with a 1064 nm fiber laser with a power of 10 W and a beam diameter of 0.025 mm at a pulse frequency of 50 - 100 kHz, where the laser moved on the plate at a speed of 2000 mm / s.

[0046] The plate was subjected to infrared spectroscopic analysis. Figure 1 The absorption spectra are shown, where the three lower curves correspond to the measured values of the samples treated by laser, while the upper curve corresponds to the measured values of the samples not treated by laser. It is obvious that the IR absorption in the measurement range is significantly reduced, making the absorption spectrum of the PA polymer visible. In the case of the untreated sample, the polymer absorption spectrum is completely covered (superimposed) by the absorption of carbon particles, making it impossible to detect the polymer.

[0047] By studying the drawings, the present disclosure, and the appended claims, those skilled in the art can understand and implement other variations of the disclosed embodiments when practicing the claimed invention.

[0048] For the processes and methods disclosed herein, the operations performed in the processes and methods may be implemented in different orders. Additionally, the operations outlined are provided only as examples, and some of them may be optional, may be combined into fewer steps and operations, may be supplemented with further operations, or may be extended into additional operations without departing from the essence of the disclosed embodiments.

[0049] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or device may fulfill the functions of several items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A polymer composition, the polymer composition comprising - a polymer, - carbon particles, and - a laser absorption additive, wherein at least a portion of the surface of the polymer composition absorbs less infrared radiation than the bulk.

2. The polymer composition according to claim 1, wherein The absorbance of infrared radiation of the at least a portion of the surface is less than 50% of the absorbance of infrared radiation of the bulk.

3. The polymer composition according to claim 1 or 2, wherein The at least a portion of the surface of the polymer composition absorbs less infrared radiation having a wavelength of 1.5 to 2.5 µm.

4. The polymer composition according to any one of claims 1 to 3, wherein, The laser absorption additive is in the form of particles and contains a metal or metalloid salt.

5. The polymer composition according to any one of claims 1 to 4, wherein, The laser absorption additive contains Fe3O4 supported on mica.

6. The polymer composition according to any one of claims 1 to 5, wherein, The polymer composition comprises 80% to 99.98% by weight of a polymer, 0.01% to 10% by weight of carbon particles, and 0.01% to 10% by weight of a laser absorption additive.

7. An article, the article comprising the polymer composition according to any one of claims 1 to 6.

8. The article according to claim 7, wherein, The article is a part of a vehicle.

9. The article according to claim 7 or 8, wherein, The article comprises a label indicating the portion of the surface of the polymer composition having a reduced absorbance of infrared radiation.

10. A method for reducing the infrared absorbance at the surface of a polymer composition containing carbon particles, the method comprising a. providing a polymer composition containing a polymer, carbon particles and a laser absorption additive, and b. exposing at least a portion of the polymer composition to laser radiation.

11. The method according to claim 10, wherein, The laser radiation has a wavelength of 800 nm to 1200 nm.

12. The method according to claim 10 or 11, wherein The laser radiation has a power / surface area of 3 to 100 kW / mm 2 .

13. Use of a laser absorption additive for reducing the infrared absorbance at the surface of a polymer composition containing carbon particles.

14. The use according to claim 13, wherein, The laser absorption additive is used to enable infrared spectroscopic analysis of a polymer composition containing carbon particles for recycling.

15. Use of the polymer composition according to any one of claims 1 to 6 or the article according to any one of claims 7 to 9 for plastic sorting based on infrared spectroscopy.

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