Decolorization of polyolefins in the molten state

Abstract

The present invention relates to a method for decolorizing a polyolefin composition, comprising the steps of: a) providing a polyolefin composition comprising at least one polyolefin and at least one organic chromophore, b) mixing the polyolefin composition in a molten state at a temperature of 170° C. to 290° C. with an inorganic oxidizing agent, wherein the inorganic oxidizing agent is selected from the group of inorganic peroxides and hypochlorites, and c) obtaining a decolorized polyolefin composition.

Description

[0001] The present invention relates to a method for decolorizing a polyolefin composition comprising a polyolefin and an organic chromophore. The present invention also relates to a decolorized polyolefin composition obtained by the method according to the present invention, and to the use of an inorganic oxidizing agent for decolorizing a polyolefin composition. Finally, the present invention relates to a method for recycling a polyolefin composition.

[0002] The recycling of plastics, and in particular of waste plastics, is a major issue today in terms of environmental protection, energy conservation and resource conservation. There are different well-known plastic recycling routes, including mechanical recycling (i.e. material sorting), advanced physical or solvent-based recycling and chemical processing (e.g. thermochemical recycling, such as pyrolysis or gasification and solvent decomposition). Of these methods, mechanical recycling is the most widely used. One of the persistent problems in the mechanical recycling of thermoplastic polymers is the removal of color so that they can be used again in full color scale.

[0003] The removal of surface layers of protective color varnishes from the surface of plastic parts, such as automotive parts, or the removal of ink-based printing elements from the surface of plastic parts, such as packaging items, can in principle be achieved, for example, by washing with organic solvents in combination with other chemicals and / or mechanical methods.

[0004] However, a particular problem is the removal of inorganic pigments, such as TiO2 or other mineral pigments, and / or organic chromophores from the bulk of plastic materials and waste plastics. The reason is that inorganic pigments and / or organic chromophores are not only present on the surface of the plastic or plastic parts, but are also distributed in the bulk of the plastic material or part. Removal of organic chromophores usually requires decomposition of the coloring substances by chemical methods.

[0005] Although offering the lowest entropy losses and energy input requirements, mechanical recycling of thermoplastic polymers presents several limitations in terms of the characteristics and properties of the resulting products. In addition to foreign polymeric and non-polymeric contaminants that limit the mechanical properties, problems arise with regard to odor and emissions as well as pigmentation. In the absence of effective color removal methods, only intensive color sorting can produce natural or at least brightly colored recyclates in mechanical processes, but limits the available quantities. Otherwise, only dark-colored recycled polymer materials are obtained.

[0006] The general expectation of the prior art recycling methods is to provide a virgin polymer, i.e. a polymer that is very similar, ideally identical, to the newly polymerized polymer in its structure and properties. Therefore, it is of great significance to develop a suitable method for removing or decomposing organic chromophores from the printing and coloring of plastic materials and waste plastics. Preferably, the method and the chemical agents involved should not destroy the chain structure of the polymer to be recycled, i.e. should not cause significant degradation.

[0007] US2006 / 0148914 relates to the use of chemical compositions that can be used to decolorize recycled thermoplastics, such as oxidants, reductants or photoinitiators combined into thermoplastics, such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC), polyethylene (PE), polylactic acid (PLA), nylon, PET copolymers, acrylic resins, Surlyn (TM) or other thermoplastics. In one example, a free radical initiator containing a peroxide compound helps to achieve decolorization of the thermoplastic. No information is given about changes or retention of polymer structure.

[0008] It is therefore an object of the present invention to provide a process for decolorizing a colored polyolefin composition, in particular for decolorizing the bulk of a colored polyolefin composition.

[0009] Another object of the present invention is to provide a method for decolorizing colored polyolefin compositions, wherein not only organic chromophores present in the polyolefin composition are removed and / or decomposed, but also while maintaining or not significantly degrading the chain structure of the polyolefin.

[0010] The present invention provides a method for decolorizing a polyolefin composition, the method comprising the following steps:

[0011] a) providing a polyolefin composition comprising at least one polyolefin and at least one organic chromophore,

[0012] b) mixing the polyolefin composition in a molten state at a temperature of 170° C. to 290° C. with an inorganic oxidizing agent, wherein the inorganic oxidizing agent is selected from the group of inorganic peroxides and hypochlorites,

[0013] c) obtaining a decolorized polyolefin composition.

[0014] In the present invention, it has surprisingly been found that an inorganic oxidizing agent selected from the group of inorganic peroxides and hypochlorites is able to decompose organic chromophores commonly used for printing and coloring of polymers, especially in the molten state. The decomposition of the organic chromophores leads to a significant lightening, leaving only a very bright yellow hue in the worst case. This decolorization significantly increases the value of the polymer material for recycling purposes.

[0015] It was further surprisingly found that, at the same time, the polymer chain structure of the polyolefin is affected much less than with organic peroxides, while providing better color removal. This means that in the case of polypropylene materials the process can be carried out in the molten state without significant degradation, and in the case of polyethylene materials no crosslinking will occur either. In other words, the method of the invention allows the structural quality of the decolorized polyolefin to be maintained, or at least not significantly reduced.

[0016] As used herein, the variation of the melt flow rate (MFR2) of the polyolefin composition before and after the decolorization process is used as an indication of the degradation of the polyolefin polymer chain. The smaller the variation of MFR2, the smaller the degradation of the polymer chain. As further used herein, the variation of the oxidation induction time (OIT) of the polyolefin composition before and after the decolorization process is used as an indication of the thermal stability of the polyolefin composition. The smaller the variation of OIT, the better the maintenance of long-term stability.

[0017] In step a) of the process according to the invention, a polyolefin composition comprising a polyolefin and an organic chromophore is provided.

[0018] The polyolefin composition comprises at least one polyolefin. In other words, the polyolefin composition may comprise one polyolefin, or two or more polyolefins that are different from each other. Preferably, the polyolefin has a relative humidity of 860 kg / m 3 Up to 960kg / m 3 and / or a melting temperature Tm of 60°C to 170°C measured according to ISO 11357-3.

[0019] Preferably, the polyolefin is selected from polyolefins having a density of 860 kg / m 3 Up to 960kg / m 3 Ethylene homopolymer or copolymer (PE), density 900kg / m 3 Up to 910kg / m 3 The present invention relates to a group of propylene homopolymers or copolymers (PP), or mixtures thereof.

[0020] Preferably, the ethylene homo- or copolymer (PE) has a melting point Tm of 60 to 135°C.

[0021] Preferably the propylene homo- or copolymer (PP) has a melting point Tm of more than 135 °C to 170 °C.

[0022] Preferably, the ethylene homopolymer or copolymer (PE) is a polymer having a density of 940 kg / m 3 Up to 960kg / m 3 High-density polyethylene (HDPE), density 900kg / m 3 Less than 940kg / m 3 Low-density polyethylene (LDPE) with a density of 900kg / m 3 Less than 940kg / m 3 Linear low-density polyethylene (LLDPE), density 860kg / m 3 Up to 890kg / m 3Polyethylene (PE) plastomers, also known as very low density (VLDPE) or ultra low density (ULDPE) polyethylene, are a special form of linear low density polyethylene (LLDPE) with a higher concentration of short chain branches, thus resulting in 860 kg / m 3 Up to 890kg / m 3 of very low density.

[0023] Preferably, the propylene homo- or copolymer (PP) is a propylene homopolymer, a random copolymer with ethylene and / or C4 to C10 α-olefins, a heterophasic copolymer with ethylene and / or C4 to C10 α-olefins, a random heterophasic copolymer with ethylene and / or C4 to C10 α-olefins, or a mixture thereof.

[0024] The polyolefin composition further comprises at least one organic chromophore. In other words, the polyolefin composition may comprise one organic chromophore, or two or more organic chromophores that are different from each other. The organic chromophore is a carbon-based chromophore.

[0025] Preferably, the organic chromophore comprises one or more azo groups, more preferably one azo group, or the organic chromophore comprises a substituted isoindoline group. The organic chromophore comprising a substituted isoindoline group preferably further comprises one, more preferably two barbituric acid groups. The organic chromophore can also be a mixture of one or more organic chromophores comprising one or more azo groups and one or more organic chromophores comprising a substituted isoindoline group.

[0026] The organic chromophore preferably comprises one or more azo groups, more preferably one azo group. Preferably, the organic chromophore comprises or consists of: disodium 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate, trisodium (4E)-3-oxo-4-[(4-sulfonato-1-naphthyl)hydrazono]naphthalene-2.7-disulfonate, 4-[[2-methoxy-5-[(phenylamino)carbonyl]phenyl]azo]-; n-(2,3-dihydro-2-oxo-1h-benzo imidazol-5-yl)-3-hydroxy-2-naphthamide, 4-[(2,5-dichlorophenyl)diazenyl]-N-[4-[[4-[(2,5-dichlorophenyl)diazenyl]-3-hydroxynaphthalene-2-carbonyl]amino]phenyl]-3-hydroxynaphthalene-2-carboxamide, trisodium 5-hydroxy-1-(4-sulfonatophenyl)-4-[(E)-(4-sulfonatophenyl)diazenyl]-1H-pyrazole-3-carboxylate and mixtures thereof.

[0027] Alternatively, the organic chromophore preferably comprises a substituted isoindoline group, more preferably a substituted isoindoline group, and further comprises one, more preferably two barbituric acid groups. Preferably, the organic chromophore comprises or consists of 5,5'-(1H-isoindole-1,3(2H)-diylidene)dibarbituric acid. Mixtures of such organic chromophores comprising substituted isoindoline groups and the above-mentioned organic chromophores comprising azo groups are also possible.

[0028] The above organic chromophore is also known in the art as "Allura Red" (6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate disodium, CAS No.25956-17-6), "Amaranth" ((4E)-3-oxo-4-[(4-sulfonato-1-naphthyl)hydrazono]naphthalene-2,7-disulfonic acid trisodium, CAS No.915-67-3), "Pigment Yellow 139" (5,5'-(1H-isoindole-1,3(2H)-diylidene) dibarbituric acid, CAS No.36888-99-0), "Pigment Red 176" (4-[[2-methoxy-5-[(phenylamino)carbonyl]phenyl]azo]-; n-(2,3-dihydro-2-oxo-1h-benzimidazol-5-yl)-3-hydroxy-2-naphthamide, CAS No.12225-06-8), "Pigment Red 166" (4-[(2,5-dichlorophenyl)diazenyl]-N-[4-[[4-[(2,5-dichlorophenyl)diazenyl]-3-hydroxynaphthalene-2-carbonyl]amino]phenyl]-3-hydroxynaphthalene-2-carboxamide, CAS No.3905-19-9) and "Tartrazine E102" (5-hydroxy-1-(4-sulfonatophenyl)-4-[(E)-(4-sulfonatophenyl)diazenyl]-1H-pyrazole-3-carboxylic acid trisodium, CAS No.1934-21-0), and all are commercially available.

[0029] Preferably, the organic chromophore is present in an amount of 1 to 100000 ppm by weight, more preferably 5 to 50000 ppm by weight, most preferably 10 to 25000 ppm by weight, based on the total polyolefin composition of step a).

[0030] In step b), the polyolefin composition is mixed with the inorganic oxidant in a molten state at a temperature of 170° C. to 290° C. The molten state means that the polyolefin composition is at least partially molten, preferably completely molten. The polyolefin composition in a molten state not only allows the polyolefin composition to be fully mixed with the inorganic oxidant, but also allows the inorganic oxidant to penetrate and / or diffuse into the bulk of the polyolefin composition, thereby being able to remove and / or decompose the organic chromophore.

[0031] The inorganic oxidizing agent is selected from the group of inorganic peroxides and hypochlorites, preferably the inorganic oxidizing agent is selected from hypochlorites. The inorganic oxidizing agent has the purpose of decolorizing the polyolefin composition, usually by decomposing the organic chromophores contained in the polyolefin composition.

[0032] According to one embodiment of the present invention, the inorganic oxidizing agent comprises an inorganic peroxide, more preferably consists of an inorganic peroxide. The inorganic peroxide is preferably selected from H2O2, a peroxyacid or a mixture thereof. Preferably, the peroxyacid comprises peroxymonosulfuric acid, peroxydisulfuric acid, peroxynitric acid, peroxyphosphoric acid and a mixture thereof, preferably consists of peroxymonosulfuric acid, peroxydisulfuric acid, peroxynitric acid, peroxyphosphoric acid and a mixture thereof.

[0033] According to another embodiment of the present invention, the inorganic oxidizing agent comprises hypochlorite, more preferably consists of hypochlorite. The hypochlorite comprises Ca(OCl)2, NaOCl, KClO, LiClO or a mixture thereof or consists thereof, most preferably the hypochlorite comprises Ca(OCl)2 or consists of Ca(OCl)2.

[0034] Preferably, the inorganic oxidizing agent in step b) is added in an amount ranging from 0.1 wt% to 10 wt%, more preferably from 0.3 wt% to 9 wt%, relative to the total polyolefin composition of step a).

[0035] Preferably, the inorganic oxidizing agent in step b) is added as an aqueous solution. This is especially true when the inorganic oxidizing agent is a hypochlorite such as Ca(OCl)2.

[0036] The mixing in step b) is preferably carried out by mechanical means, such as a mixer, a kneader or an extruder. Preferably, the mixing in step b) is carried out for 30 seconds to 600 seconds.

[0037] Preferably, the process is a continuous process or a batch process.

[0038] According to one embodiment of the invention, the process is a continuous process and step b) is carried out in an extruder, preferably in a single-screw or twin-screw extruder. Preferably, the continuous process further comprises a degassing and / or granulation step after step b).

[0039] According to another embodiment of the invention, the process is a discontinuous process and step b) is carried out in a kneader, preferably a chamber kneader or a Farell kneader.

[0040] Polymer materials and polymer wastes generally contain one or more additives, which affect the material properties of the polymer materials. Preferably, the polyolefin composition further comprises an additive. The additive preferably comprises one or more stabilizers and / or one or more modifiers. Preferably, the stabilizer is selected from an antioxidant, a UV stabilizer or a combination thereof. Antioxidants generally include sterically hindered phenols and / or phosphites or phosphonites. Preferably, the modifier is selected from acid scavengers, slip agents, antiblocking agents, foaming agents, nucleating agents and biocides. Such additives are well known in the art.

[0041] In step c) of the process according to the invention, a decolorized polyolefin composition is obtained.The decolorized polyolefin composition may comprise decomposition products of organic chromophores.

[0042] The decolorization of polyolefin composition is measured by colorimetry according to ISO 11664-4 and described in more detail below.Euclidean distance Δ E is a measure of the decolorization of polyolefin composition.In other words, Δ E is the color difference between the colored polyolefin composition provided in step a) of the method according to the present invention and the decolorized polyolefin composition obtained in step c).Preferably, the Δ E of the decolorized polyolefin composition measured according to ISO 11664-4 is between 6.0 and 120.0.

[0043] Preferably, the polyolefin composition of step a) has a first MFR2 measured according to ISO 1133 of 0.1 g / 10min to 100 g / 10min and / or the bleached polyolefin composition obtained in step c) has a second MFR2 measured according to ISO 1133 of 0.1 g / 10min to 500 g / 10min.

[0044] Preferably, the polyolefin composition of step a) has a first MFR2 measured according to ISO 1133 and the bleached polyolefin composition obtained in step c) has a second MFR2 measured according to ISO 1133, wherein the second MFR2 satisfies

[0045] 1.5·(first MFR2)≥(second MFR2)≥0.9·(first MFR2)

[0046] And more preferably, the second MFR2 satisfies

[0047] 1.45·(first MFR2)≥(second MFR2)≥0.95·(first MFR2).

[0048] Preferably, the polyolefin composition of step a) has a first oxidative induction time (OIT) measured according to ISO 11357-6, and the decolorized polyolefin composition obtained in step c) has a second OIT measured according to ISO 11357-6, wherein the second OIT is equal to or less than the first OIT, more preferably, the second OIT is less than the first OIT.

[0049] The present invention also relates to a decolorized polyolefin composition obtained by the process according to the invention as described in all embodiments. If applicable, all embodiments of the process according to the invention are also embodiments of the decolorized polyolefin composition.

[0050] Preferably, the bleached polyolefin composition has an oxidative induction time (OIT) measured according to ISO 11357-6 of from 2 minutes to 60 minutes.

[0051] The present invention also relates to the use of an inorganic oxidizing agent selected from the group of inorganic peroxides and hypochlorites for decolorizing a polyolefin composition comprising at least one polyolefin and at least one organic chromophore.

[0052] If applicable, all embodiments of the polyolefin composition and the inorganic oxidizing agent described herein are also preferred embodiments of the use according to the present invention.

[0053] Finally, the present invention relates to a process for recycling a polyolefin composition comprising at least one polyolefin and at least one organic chromophore, said recycling process comprising the process for decolorizing a polyolefin composition according to the present invention as described herein in all embodiments.

[0054] All embodiments of the process for decolorizing a polyolefin composition as described herein are also embodiments of the process for recycling a polyolefin composition.

[0055] Preferably, the method for recovering the polyolefin composition also comprises step a0): collecting and sorting plastics, particularly waste plastics, thereby providing a polyolefin composition comprising at least one polyolefin and at least one organic chromophore for the step a) of the method for decolorizing the polyolefin composition. Therefore step a0) occurs before step a). Sorting refers to separating the plastics and / or waste plastics made of the colored polyolefin composition from the plastics and / or waste plastics made of colored or colorless non-polyolefin compositions such as polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET) and polyamide (PA) to achieve high purity. Sorting methods suitable for this are generally known in the art from the mechanical recovery of plastics and waste plastics.

[0056] Preferably, the method for recovering a polyolefin composition further comprises a step d) of subjecting the decolorized polyolefin composition obtained in step c) to downstream processing. Thus, step d) occurs after step c). Preferably, the downstream processing comprises degassing, pelletizing, removing additives and / or decomposition products of organic chromophores from the decolorized polyolefin composition, forming an article from the decolorized polyolefin composition, or a combination thereof.

[0057] The present invention is further illustrated below by way of non-limiting examples. Example

[0058] 1. Measurement method

[0059] a) Melt flow rate

[0060] The melt flow rate (MFR) is determined according to ISO 1133 and is expressed in g / 10 min. The higher the melt flow rate, the lower the viscosity of the polymer.

[0061] The MFR of polyethylene is measured at 190° C. and 2.16 kg load (MFR2), and the MFR of polypropylene is measured at 230° C. and 2.16 kg load (MFR2).

[0062] b) Density

[0063] The density of the polymers was measured according to ISO 1183-1:2004 (Method A) on compression molded test specimens prepared according to EN ISO 1872-2 (February 2007) and is reported in kg / m 3 Given.

[0064] c) Decolorization

[0065] The Euclidean distance ΔE is calculated according to EN ISO 11664-4 using the following formula:

[0066]

[0067] where L is the CIELAB lightness and a and b are the CIELAB coordinates, see EN ISO 11664-4.

[0068] The higher the ΔE, the more decolorized the sample is.

[0069] d) OIT measurement

[0070] The oxidation induction time (OIT) at 200°C was determined using a TA Instrument Q20 according to ISO 11357-6. The instrument was calibrated using indium and tin according to ISO 11357-1. The maximum error in temperature after calibration was less than 0.1 K. Each polymer sample weighing 10±2 mg (cylindrical geometry with a diameter of 5 mm and a thickness of 1±0.1 mm) was placed in an open aluminum crucible and heated in nitrogen (>99.95% by volume N2, <5 ppm O2) at 20°C min –1 The heating rate was from 25°C to 200°C, and the gas flow rate was 50 mL min –1 , and allowed to rest for 5 min before switching the atmosphere to pure oxygen (>99.95 vol% O2) at a flow rate of 50 mL min –1 The sample was maintained at a constant temperature and the exotherm associated with the oxidation was recorded. The oxidation induction time is the time interval between the start of the oxygen flow and the onset of the oxidation reaction. Each presented data point is the average of three independent measurements.

[0071] e) Melting temperature

[0072] Data were measured using a TA Instrument Q2000 Differential Scanning Calorimetry (DSC) on 5 to 7 mg samples. The DSC was run according to ISO 11357 / Part 3 / Method C2 in a heating / cooling / heating cycle at a scan rate of 10°C / min over a temperature range of -30 to +225°C. The melting temperature (Tm) was determined from the second heating step.

[0073] 2. Materials

[0074] a) Organic chromophore

[0075] AR: Temptation Red

[0076] (6-Hydroxy-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate disodium salt, CAS No. 25956-17-6)

[0077] Ama: Amaranth

[0078] ((4E)-3-oxo-4-[(4-sulfonato-1-naphthyl)hydrazono]naphthalene-2,7-disulfonate trisodium salt, CAS No. 915-67-3)

[0079] PY139: Pigment Yellow 139

[0080] (5,5'-(1H-isoindole-1,3(2H)-diylidene) dibarbituric acid, CAS No.36888-99-0)

[0081] NCl a: Pigment Red 176

[0082] (4-[[2-methoxy-5-[(phenylamino)carbonyl]phenyl]azo]-; n-(2,3-dihydro-2-oxo-1h-benzimidazol-5-yl)-3-hydroxy-2-naphthamide, CAS No.12225-06-8)

[0083] NCl b: Pigment Red 166

[0084] (4-[(2,5-dichlorophenyl)diazenyl]-N-[4-[[4-[(2,5-dichlorophenyl)diazenyl]-3-hydroxynaphthalene-2-carbonyl]amino]phenyl]-3-hydroxynaphthalene-2-carboxamide, CAS No.3905-19-9)

[0085] Tar:Tartrazine E102

[0086] (5-hydroxy-1-(4-sulfonatophenyl)-4-[(E)-(4-sulfonatophenyl)diazenyl]-1H-pyrazole-3-carboxylic acid trisodium, CAS No. 1934-21-0)

[0087] b) Polymer

[0088] PP contains MFR2 of 12g / 10min and density of 905kg / m 3 A composition of a polypropylene homopolymer of 0.072 wt. % Irganox B215 (a 2:1 blend of Irgafos 168, CAS-No. 31570-04-4 and Irganox 1010, CAS-No. 6683-19-8, commercially available from BASF AG, Germany as a process and long-term heat stabilizer) and 0.04 wt. % calcium stearate (CAS-No. 1592-23-0).

[0089] LDPE is a low-density polyethylene with an MFR2 of 4g / 10min, a melting temperature Tm of 111°C, and a density of 922kg / m 3 .

[0090] c) Oxidants

[0091] Calcium hypochlorite Ca(OCl)2 was used as a solution in deionized water with a concentration of 0.5 mol / l (0.5 M solution).

[0092] Dicumyl peroxide (DCP), CAS-No. 80-43-3, is used in the form of solid powder.

[0093] 3. Results

[0094] a) Batch Kneader Example

[0095] The volume is 50cm 3 The chamber of the Brabender Plasticorder twin-rotor chamber kneader (Brabender, Germany) was flushed with nitrogen (2.5 L / min) from the beginning, and the screw speed was 40 rpm. The temperature was set to 195° C. using a Lauda Proline P5 oil thermostat. 35 g of a dry blend based on polymer and chromophore was added to the chamber and mixed for 2.5 minutes. Thereafter, an oxidant in the amount given in Table 1 below was added. The dry blend with the oxidant was kneaded for 2.5 minutes, then collected and pressed with a hot press and cooled. Color and gloss measurements were then performed with white paper as background. The details of the batch kneader embodiment are given in Table 1 below.

[0096] Table 1: Batch kneading machine example

[0097]

[0098]

[0099] *In alcohol with adjuvant

[0100] **In the water

[0101] DCP dicumyl peroxide

[0102] MFR (2.16 kg), OIT and the parameters L, a, b for colorimetry were measured before (index "0") and after (index "D") bleaching. ΔMFR, ΔE, ΔOIT are the changes in MFR, E, OIT before and after bleaching of the example. The results are given in Table 2 below.

[0103] Table 2: Measurements and results

[0104] <![CDATA[MFR0]]> <![CDATA[OIT0]]> <![CDATA[L0]]> <![CDATA[a0]]> <![CDATA[b0]]> <![CDATA[L D ]]> <![CDATA[a D ]]> <![CDATA[b D ]]> ΔE <![CDATA[MFR D ]]> <![CDATA[OIT D ]]> g / 10min min - - - - - - - g / 10min min IE1 11 9.7 49.4 29.2 18.4 57.3 5.7 4.6 28.4 13.8 4.2 IE2 11 9.7 51.0 7.8 5.6 40.7 11.1 3.5 11.0 16 3.8 IE3 11 9.7 57.7 11.5 20.3 57.3 14.9 26.7 7.3 16 3.8 IE4 3.9 36.8 44.5 29.9 25.1 39.5 5.2 4.7 32.4 3.9 17.6 IE5 3.9 36.8 44.5 29.9 25.1 25.7 4.9 4.2 37.6 4.0 10.1 IE6 3.9 36.8 54.0 9.4 3.4 47.5 11.9 3.1 7.0 4.0 10.1 IE7 3.9 36.8 46.0 8.5 1.2 38.9 10.1 1.0 7.3 4.0 10.1 IE8 3.9 36.8 46.0 8.5 1.2 36.5 11.2 0.9 9.9 4.1 9.9 CE1 11 9.7 42.9 9.0 4.0 40.8 11.1 3.5 3.0 45 1.1 CE2 11 9.7 44.3 13.2 12.2 45.0 13.4 7.8 4.5 45 1.1 CE3 3.9 36.8 52.0 6.1 1.6 56.9 6.4 0.6 5.0 3.3 0.7 CE4 3.9 36.8 46.0 7.5 1.2 45.5 8.7 1.2 1.3 3.3 0.7

[0105] Table 2 (continued)

[0106]

[0107]

[0108] As can be seen from Table 2 above, for PP and LDPE samples, the ΔOIT of the examples of the present invention is lower than that of the comparative examples. This indicates that the stability loss of the examples of the present invention is lower than that of the comparative examples.

[0109] b) Extruder Example

[0110] A small TSE 24MC twin screw extruder (Thermofisher, UK) with a barrel diameter of 24 mm and an L / D ratio of 40 was used, equipped with a high strength screw design with three kneading zones. The polymer and pigment were fed as a dry blend through a hopper in the amounts given in Table 3 below, and a 0.5 M oxidant solution was fed through the feed port between the first and second kneading blocks. Downstream atmospheric degassing was used. The extruder was set at a constant barrel temperature of 190°C, using a screw speed of 300 rpm and a filling factor of 40-60% and a throughput of 6 kg / h. The resulting melt strands from the triple die were solidified in a water bath and subsequently pelletized. Details of the extruder embodiment are given in Table 3 below.

[0111] Table 3: Extruder Examples

[0112] polymer pigment quantity concentration Oxidants concentration type type weight% Weight ppm type weight% IE9 PP NCI a&b 0.10* 100 <![CDATA[Ca(OCl)2]]> 0.6 IE10 PP NCI a&b 0.05* 50 <![CDATA[Ca(OCl)2]]> 0.6 IE11 LDPE NCI a&b 1.00* 1000 <![CDATA[Ca(OCl)2]]> 0.6 IE12 LDPE NCI a&b 0.50* 500 <![CDATA[Ca(OCl)2]]> 0.6 IE13 LDPE NCI a&b 0.10* 100 <![CDATA[Ca(OCl)2]]> 0.6 IE14 LDPE NCI a&b 0.05* 50 <![CDATA[Ca(OCl)2]]> 0.6

[0113] *In alcohol with adjuvant

[0114] MFR (2.16 kg), OIT and the parameters L, a, b for colorimetry were measured or determined before (index "0") and after (index "D") bleaching. ΔMFR and ΔE are the changes in MFR and E before and after bleaching of the sample. The results are given in Table 4 below.

[0115] Table 4: Measurements and results

[0116]

[0117]

Claims

1. A method for decolorizing a polyolefin composition, the method comprising the steps of: a) providing a polyolefin composition comprising at least one polyolefin and at least one organic chromophore, b) mixing the polyolefin composition in a molten state at a temperature of 170° C. to 290° C. with an inorganic oxidant, wherein the inorganic oxidant is hypochlorite, c) obtaining a decolorized polyolefin composition, wherein the organic chromophore comprises one or more azo groups, or wherein the organic chromophore comprises a substituted isoindoline group, The polyolefin is selected from a polyolefin having a density of 860 kg / m 3 Up to 960kg / m 3 Ethylene homopolymer or copolymer, density 900kg / m 3 Up to 910kg / m 3 The present invention relates to a group of propylene homopolymers or copolymers, or mixtures thereof.

2. The method of claim 1, wherein the polyolefin has a hardness of 860 kg / m 3 Up to 960kg / m 3 and / or a melting temperature Tm of 60°C to 170°C measured according to ISO 11357-3.

3. The method according to claim 1, wherein the ethylene homopolymer or copolymer is a polymer having a density of 940 kg / m 3 Up to 960kg / m 3 HDPE, density is 900kg / m 3 Less than 940kg / m 3 LDPE, density is 900kg / m 3 Less than 940kg / m 3 LLDPE, density is 860kg / m 3 Up to 890kg / m 3 plastics, or mixtures thereof.

4. The method according to claim 1, wherein the propylene homopolymer or copolymer is a propylene homopolymer, a random copolymer with ethylene and / or C4 to C10 α-olefins, a heterophasic copolymer with ethylene and / or C4 to C10 α-olefins, a random heterophasic copolymer with ethylene and / or C4 to C10 α-olefins, or a mixture thereof.

5. The method according to any one of claims 1 to 4, wherein the organic chromophore comprises disodium 6-hydroxy-5-[(2-methoxy-5-methyl-4-sulfonatophenyl)diazenyl]naphthalene-2-sulfonate, trisodium (4E)-3-oxo-4-[(4-sulfonato-1-naphthyl)hydrazono]naphthalene-2,7-disulfonate, 4-[[2-methoxy-5-[(phenylamino)carbonyl]phenyl]azo]-; n-(2,3-dihydro-2-oxo-1h-benzimidazol-5-yl)- 3-Hydroxy-2-naphthamide, 4-[(2.5-dichlorophenyl)diazenyl]-N-[4-[[4-[(2.5-dichlorophenyl)diazenyl]-3-hydroxynaphthalene-2-carbonyl]amino]phenyl]-3-hydroxynaphthalene-2-carboxamide, trisodium 5-hydroxy-1-(4-sulfonatophenyl)-4-[(E)-(4-sulfonatophenyl)diazenyl]-1H-pyrazole-3-carboxylate, 5,5'-(1H-isoindole-1,3(2H)-diylidene)dibarbituric acid and mixtures thereof.

6. The process according to any one of claims 1 to 4, wherein the organic chromophore is present in an amount of 1 to 100000 ppm by weight, based on the total polyolefin composition of step a).

7. The process according to claim 6, wherein the organic chromophore is present in an amount of 5 to 50000 ppm by weight, based on the total polyolefin composition of step a).

8. The process according to claim 6, wherein the organic chromophore is present in an amount of 10 to 25000 ppm by weight, based on the total polyolefin composition of step a).

9. The method according to any one of claims 1 to 4, wherein the inorganic oxidizing agent is hypochlorite, and the hypochlorite comprises Ca(OCl)2, NaOCl, KClO, LiClO or a mixture thereof.

10. The method according to any one of claims 1 to 4, wherein the inorganic oxidizing agent in step b) is added in an amount of 0.1 to 10 wt% relative to the total polyolefin composition of step a).

11. The process according to any one of claims 1 to 4, wherein the bleached polyolefin composition has a ΔE measured according to ISO 11664-4 of between 6.0 and 120.

0.

12. The process according to any one of claims 1 to 4, wherein the polyolefin composition of step a) has a first MFR2 measured according to ISO 1133 and the bleached polyolefin composition obtained in step c) has a second MFR2 measured according to ISO 1133, wherein the second MFR2 satisfies 1.5·(first MFR2)≥(second MFR2)≥0.9·(first MFR2).

13. Decolorized polyolefin composition obtainable by the process according to any one of claims 1 to 12.

14. Use of hypochlorites for decolorizing polyolefin compositions comprising at least one polyolefin and at least one organic chromophore, wherein the organic chromophore comprises one or more azo groups, or wherein the organic chromophore comprises a substituted isoindoline group, The polyolefin is selected from a group consisting of polyolefins having a density of 860 kg / m 3 Up to 960kg / m 3 Ethylene homopolymer or copolymer, density 900kg / m 3 Up to 910kg / m 3 The present invention relates to a group of propylene homopolymers or copolymers, or mixtures thereof.

15. Process for recycling a polyolefin composition comprising at least one polyolefin and at least one organic chromophore, said recycling process comprising the process for decolorizing a polyolefin composition according to any one of claims 1 to 12.

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