Method and apparatus for removing impurities from an extrudable material containing impurities

Abstract

A method of extruding a recycled polymer from an extrudable material containing impurities, the method comprising injecting a non-solvent in a liquid state into a device, and mixing the non-solvent substantially homogeneously with the extrudable material containing impurities, thereby forming a dispersion of the non-solvent and the extrudable material containing impurities, and the impurities are discharged from the device in a gaseous state.

Description

Technical Field

[0001] The present invention includes a method, an apparatus, and a recycled polymer for extruding a recycled polymer from an extrudable material containing impurities.

Background Art

[0002] Methods for polymer recycling and methods including removal or purification of contaminants in the recycled polymer are known from a number of patent applications. For example, International Publication No. 2021 / 123475 (Patent Document 1) teaches a method for removing contaminants from recycled plastics, for example, a method for purifying polyethylene (PE), polypropylene (PP), or polyester (PET) from plastic waste. The method disclosed therein comprises mixing a recycled plastic polymer containing organic contaminants in an extractor using a water-soluble solvent. Subsequently, a centrifugation step is applied to the mixture of the recycled plastic polymer and the water-soluble solvent, thereby enabling the transport of the organic contaminants contained in the recycled plastic polymer into the liquid-phase water-soluble solvent.

[0003] International Publication No. 2020 / 245476 (Patent Document 2) teaches a method for removing volatile organic components having an odor in recycled plastics. This method includes injecting gaseous water (steam) into a distillation column containing the recycled plastic. The volatile organic components are extracted from the recycled plastic by distillation, and then the volatile organic components are discharged together with water / steam through the upper part of the distillation column.

[0004] A method for extruding a low-odor polyphenylene ether resin and a polystyrene resin from a solution containing a polyphenylene ether resin and a polystyrene resin is described in European Patent Application Publication No. 0377115 (Patent Document 3). The method for extruding a polyphenylene ether resin and a polystyrene resin includes a first step of mixing a solution containing a polyphenylene ether resin and a liquid aromatic hydrocarbon solvent in a first apparatus. The second step includes heating the liquid polymer solution to discharge a volatile first fraction in gaseous form. This second step results in a partially devolatilized polymer solution. The partially devolatilized polymer solution is then transported to a second apparatus. Vapor or water is injected into the partially devolatilized polymer solution, and a second fraction of impurities is discharged from the partially devolatilized polymer solution.

[0005] International Publication No. 2006 / 097470 (Patent Document 4) teaches a method for removing residual styrene monomer from a blend containing polystyrene and polyvinylpyrrolidone. This method includes mixing a blend containing polystyrene and polyvinylpyrrolidone with water in a container. Vapor is injected into the container containing polystyrene, polyvinylpyrrolidone, and water, and at the same time, water is removed by concentration. In one aspect of this method, instead of injecting water into the container containing polystyrene, polyvinylpyrrolidone, and water, a stream of an inert gas such as nitrogen or argon is injected.

[0006] JP-A-2002 / 097362 (Patent Document 5) describes a method for producing a resin for a mold having high odor characteristics. This resin is a virgin polymer used for electronic components. This method includes introducing a polyphenylene ether-based resin and a polystyrene-based resin into an extruder and melt-kneading the polyphenylene ether-based resin and the polystyrene-based resin. Liquid water is injected into the extruder. The polyphenylene ether-based resin and the polystyrene-based resin are subjected to a degassing step. This degassing step makes it possible to remove odors from the polyphenylene ether-based resin and the polystyrene-based resin. This odor is a residual monomer contained in the polyphenylene ether-based resin, an oligomer contained in the polystyrene-based resin, and a volatile component. This volatile component is, for example, a volatile component or by-product generated by the separation of the polystyrene-based resin during reduced pressure. This volatile component is, in a further example, styrene monomer, 2,4,6-trimethylanisole, 7-methyldihydrobenzofuran, 2,3-dihydrobenzofuran, toluene, or ethylbenzene.

[0007] DE-A-808788 (Patent Document 6) relates to a method for improving the properties of a polystyrene or styrene copolymer containing volatile organic components. This method includes floating a polystyrene or styrene copolymer in the form of beads or granules in water in a closed container. Steam is injected into the container. Then, this steam in the container is discharged from the container, and the transport of the volatile organic components into the steam is possible.

[0008] Japanese Patent Application Laid-Open No. 3840293 (Patent Document 7) discloses a method for removing impurities of monomers and / or oligomers from components produced by polymerization. This component is a virgin polymer, and this method includes using an extractant that is supercritical carbon dioxide. However, since it is expensive and difficult to maintain supercritical carbon dioxide in a supercritical state, the method disclosed in this application is not economical.

[0009] U.S. Patent No. 4790517 (Patent Document 8) discloses a method and apparatus for producing a thermoplastic resin composition. The thermoplastic resin composition is any one of a polymer alloy, a polymer blend, and a mixture of a thermoplastic resin and a filler. This method includes supplying the thermoplastic resin composition from a supply port of the apparatus to a plasticizing section, and the thermoplastic resin composition is melted in this plasticizing section. Liquid carbon dioxide is injected into a kneading section of the apparatus, and the thermoplastic resin composition is kneaded at a high pressure of 10 MPa or more and less than about 20 MPa. This method further includes performing vacuum suction in a vacuum vent section of the apparatus through a vent port to carry out pressure reduction. This pressure reduction is a pressure gradient of 3 MPa / second or more and less than 10 GPa / second so as to remove carbon dioxide from the die of the apparatus.

[0010] U.S. Patent Application Laid-Open No. 5204410 (Patent Document 9) discloses a method for removing volatile substances from a polypropylene ether or polypropylene ether / styrene resin composition. The resin composition taught in this application is a virgin polymer and is used for food contact materials. Volatile substances are typically styrene and catalyst pieces such as trimethyl anisole, trialkylamine, toluene, methyl dihydrobenzofuran, dihydrobenzofuran, dimethyl cyclohexanone, ethyl hexenal, and various amine catalyst pieces. The method used in this patent application is not for plastic recycling. Carbon dioxide, rather than water, is proposed as an extractant. However, the combination of carbon dioxide and water is not taught in this document.

[0011] U.S. Patent Application Publication No. 5,851,065 (Patent Document 10) discloses a method and apparatus for recycling resin scraps. The resin scraps comprise a thermosetting resin paint film and a thermoplastic resin material and are fed into the path of a cylinder. Subsequently, the resin scraps are melted to form a melt, which is delivered from the upstream side to the downstream side of the cylinder path by a screw array. The thermosetting resin in the melt is hydrolyzed by a hydrolyzing agent (e.g., water). The melt forms a very enclosed area with a register that restricts the flow of the melt, thereby enhancing the contact efficiency between the resin scraps and water. As a result of this hydrolysis, the three-dimensionally cross-linked structure of the resin scraps is broken down into decomposed components. The water generated from the hydrolysis of the resin scraps is degassed by evaporating the moisture, and the decomposed components are partially discharged together with water when the water is evaporated. The method described in this document is not as efficient as the removal of impurities from a melt of virgin polymer using water. This is because the decomposed components are only poorly diffused through the melt of the recycled plastic.

[0012] European Patent Application Publication No. 0,375,937 (Patent Document 11) discloses a method for reducing impurities in a mixture. This mixture is a virgin polymer that is substantially odorless and tasteless for food contact applications. This mixture may contain polyphenylene ether resin alone or in combination with a styrene resin, and further contains impurities selected from styrene monomer, toluene, volatile oxygenated species having an odor, volatile amines having an odor, any mixture thereof, and the like. This method includes extruding the mixture at a temperature higher than the melting point of the mixture. This extrusion is performed in at least two stages in one path. These two stages include injecting water and subsequently drawing a vacuum.

[0013] International Publication No. 2012 / 108245 (Patent Document 12) discloses a method for producing virgin polymers in the form of polycarbonate resins. The pellets of this polycarbonate resin can have a reduced methylene chloride content. This method starts from a polycarbonate resin in the form of specific powders or granules and includes the step of transferring the polycarbonate resin into an inert gas atmosphere having an oxygen concentration of 3 vol% or less. The polycarbonate resin falls over 50 cm in the inert gas atmosphere. Water having an electrical conductivity of 30 μS / cm or less is injected in a specific amount into the kneading zone of an extruder. A further step of this method is to adjust the moisture concentration in the polycarbonate resin to 10 to 200 ppm by removing methylene chloride together with water from the polycarbonate resin and exhausting it through vent holes provided downstream of the kneading zone. The melt resin in strand form is extruded through a die into a water bath. This introduction of the melt resin in strand form enables the cooling of the melt resin in strand form. The melt resin in strand form is cut at 70 to 130 degrees Celsius to provide pellets. By this method, pellets having a moisture content of 10 to 200 ppm can further absorb water in a humid atmosphere, whereby the moisture content of the pellets is adjusted to a value that exceeds the initial moisture content of the pellets and is 1300 ppm or less.

[0014] Korean Patent Publication No. 2012 - 0029407 (Patent Document 13) relates to an apparatus and method for devolatilizing a polycarbonate solution containing a solvent to produce a virgin polymer of polycarbonate. This apparatus includes a devolatilizer and an extruder. This method includes injecting and mixing an inert component such as nitrogen, argon, carbon dioxide, water, methane, or helium into the polymer melt upstream of a downflow devolatilizer. The inert component is injected as an azeotropic additive in the extruder.

[0015] These prior art methods describe creating virgin polymers, i.e., new polymers, with impurity residual concentrations in the virgin polymer of up to 250 ppm. Impurities in the virgin polymer have been intentionally introduced during the manufacturing process of the virgin polymer. Impurities are, for example, used solvents and used monomers introduced during manufacturing. These intentionally introduced solvents and monomers must later be removed from the polymer melt of the virgin polymer.

[0016] The recycled polymers described in the prior art contain short-chain segments. One of the difficulties with the melt made from the recycled polymer is that "gels" are formed in the melt. Even when water is added to the melt, since it does not disperse in the polymer gel, water cannot remove the impurities contained in the polymer gel. Therefore, this melt retains these impurities when they are re-extruded.

[0017] International Publication No. 2021 / 048756 (Patent Document 14) discloses a process for the recovery and desulfurization of vulcanized rubber. Water is used to break the bonds of sulfur in the rubber. Using carbon dioxide and water together is not taught in this document.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0019] The present disclosure teaches a method for extruding a recycled polymer from an extrudable material containing impurities. The method includes injecting a non - solvent in a liquid state into a device and mixing the non - solvent substantially homogeneously with the extrudable material containing impurities, thereby forming a dispersion of the non - solvent and the extrudable material containing impurities. The non - solvent is injected into the extruder in a liquid state, thereby achieving a homogeneous liquid - state dispersion of the non - solvent and the extrudable material containing impurities. The formation of the dispersion of the non - solvent and the extrudable material containing impurities enables the simultaneous extraction of impurities from the extrudable material containing impurities and obtaining a gas phase containing the impurities and the non - solvent. Therefore, in this method, there is no need to apply two separate steps of first separating the impurities from the extrudable material containing impurities and then evaporating the impurities and the non - solvent.

[0020] In one aspect of the present invention, the recycled polymer is made from used consumer waste or industrial waste and has an impurity concentration of less than 10 ppm.

[0021] The method described in this document can purify an extrudable material containing impurities by removing a substantial portion of the impurities from the extrudable material containing impurities. The method produces a recycled polymer in which the residual impurity concentration in the recycled polymer is less than 100 ppm, and in one aspect less than 10 ppm.

[0022] Impurities in the recycled polymer are substances unintentionally introduced into the polymer waste, such as foodstuffs. It has been found that there are more than 30 different types of impurities in the recycled polymer, such as polar and non-polar impurities, protic and aprotic impurities, etc. Due to the effect of the residual impurities on the odor, taste, touch, and strength of the recycled polymer, these impurities must be removed from the recycled polymer.

[0023] The method described in this document complies with the European Commission (EC) Regulation (EU) 2022 / 1616 of 15 September 2022 regarding recycled plastic materials and articles intended to come into contact with food.

[0024] The method can use high temperature and high pressure, which means that the transport mechanism for removing the non-solvent containing impurities is accelerated. The reduction in the number of steps means that less time is required to carry out the method, and thus less solvent is required to extract the impurities from the extrudable material containing impurities. The substantial homogeneous mixing of the extrudable material containing impurities with the non-solvent enables the processing time to be accelerated, and thus a small amount of non-solvent is required to remove the impurities from the extrudable material containing impurities. The method for extruding the recycled polymer requires only a small amount of non-solvent, so it has an economic advantage and also an environmental-friendly advantage.

[0025] The non-solvent containing impurities is discharged from the extruder in a gaseous state.

[0026] The non-solvent forms a mixture with the impurities and, in one aspect, forms an azeotropic mixture with the impurities.

[0027] This non-solvent is selected from at least one of water, a mixture of water, a base, an ester, an alcohol, an ether, an alkane, or a ketone. This alcohol is selected from, for example, methanol, ethanol, or isopropanol. The base is at least one of ammonia or pyridine.

[0028] In one aspect, the non-solvent is a mixture of water and carbon dioxide, and the concentration of the carbon dioxide is between 10% and 50% as weight in water. The fact that water can remove impurities was a surprising result. This is because the prior art suggested that even when water is used in recycled plastics, water cannot be sufficiently finely dispersed in the recycled plastics and this removal cannot be achieved. Carbon dioxide is acting as a catalyst. Since carbon dioxide is easily removed from the melt, the use of carbon dioxide instead of an alternative acidic or basic catalyst is more preferable for environmental reasons. Furthermore, carbon dioxide is a residue and leaves no residue in the extruded plastic that can cause problems when the product made from the extruded plastic is brought into contact with a living body.

[0029] In one aspect, the impurities are impurities having a molecular weight of up to 500 g / mol and, in one aspect, up to 160 g / mol. Examples of impurities include, for example, one or more of carboxylic acids, aldehydes, terpenes, aromatics, olefins, alkanes, nitrogen-based compounds, phosphorus-based compounds, sulfur-based compounds, or mixtures thereof.

[0030] In one non-limiting aspect, the extrudable material containing impurities is passed through a melt filter prior to the injection of the non-solvent. Also, after the injection of the non-solvent, the extrudable material containing impurities may be passed through a melt filter. In a further aspect, two melt filters arranged before and after the injection of the non-solvent may be used.

[0031] The mixing of the extrudable material containing impurities and the non-solvent is carried out, for example, at a temperature between 110 °C and 330 °C and a pressure between 2 and 300 bar (200 - 30000 kPa).

[0032] This method further includes the steps of producing the recycled polymer in water to cool the recycled polymer and then or simultaneously cutting the polymer to form granular polymer.

[0033] Also disclosed is an apparatus for removing impurities from an extrudable material containing impurities. The apparatus comprises an injector for injecting a non-solvent in a liquid state into the extrudable material containing impurities, a mixing element for mixing the non-solvent substantially homogeneously with the extrudable material containing impurities, and a discharge device for discharging gaseous impurities from the apparatus.

[0034] The mixing element comprises a screw device within a housing. The mixing element further comprises one of a single screw or a multi-screw such as a double screw.

[0035] The screw device further comprises one of a kneading block or a toothed disk.

[0036] The apparatus comprises a heating device for heating the extrudable material containing impurities.

[0037] Also disclosed is a recycled polymer. The recycled polymer contains a polyolefin and impurities, and the individual impurities are substantially homogeneously dispersed in the recycled polymer, and the concentration of each of the individual impurities in the recycled polymer is at most 10 ppm by weight, and in a further aspect, at most 5 ppm by weight.

[0038] The polyolefin includes polyethylene or polypropylene.

[0039] The recycled polymer has low odor characteristics.

[0040] Also disclosed is a method of using the recycled polymer, for example, a method of using it in consumer packages.

Brief Description of the Drawings

[0041]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0042] Hereinafter, the present invention will be described based on the drawings. It should be understood that the embodiments and aspects of the present invention described herein are merely examples and do not limit the scope of protection of the claims in any way. The present invention is defined by the claims and their equivalents. It should be understood that the features of one aspect or embodiment of the present invention can be combined with the features of different aspects or embodiments of the present invention.

[0043] Figure 1 shows an example of an apparatus 10 for removing impurities 20 from an extrudable material 30 containing impurities. The apparatus 10 can be, for example, an extruder. The apparatus 10 includes a hopper 15, a housing 62, and a material outlet 90. The extrudable material 30 containing impurities is within the housing 62, and an injector 45 attached to the housing 62 enables injection of a non-solvent 50 in a liquid state into the extrudable material 30 containing impurities. A heating element 80 for heating the extrudable material 30 containing impurities is present in the apparatus 10.

[0044] The housing 62 surrounds a mixing element 60. The mixing element 60 enables mixing the non-solvent 50 substantially homogeneously with the extrudable material 30 containing impurities. The mixing element 60 can be a screw device 61 as shown in Figure 2, which may be a single screw or a double screw. Also, the mixing element 60 may be a kneading block 63 as shown in Figure 3, or a toothed disk as shown in Figure 4.

[0045] The apparatus 10 further includes a discharge device 70 for discharging the gaseous impurities 20 from the apparatus 10. The recycled polymer 100 is produced from the material outlet 90 into a water bath 110 filled with water. By producing the recycled polymer 100 into the water bath 110, the produced recycled polymer 100 is cooled. The recycled polymer 100 is cut into the form of granules or pellets simultaneously when it is produced into the water bath 110 or after being cooled in the water bath 110.

[0046] The apparatus 10 may also include a melt filter 40. In one aspect, the melt filter 40 is disposed in front of the injector 45 and functions to remove impurities contained in the extrudable material 30 containing impurities. The impurities can be solid contaminants, for example, fine particles, unreacted polymers, carbonized polymers, aggregated additives, and debris, such as debris like metal particles, dirt, or dust.

[0047] In another aspect, the melt filter 40 is disposed after (i.e., downstream of) the injector 45.

[0048] In the present disclosure, the term "extrudable material containing impurities" means a polymeric material that can be heated and extruded. The extrudable material 30 provided at the material inlet 15 contains a high concentration of impurities 20.

[0049] In one non-limiting example, the extrudable material containing impurities contains impurities 20 at a concentration of at least 70 ppm. In other examples, the extrudable material 30 containing impurities contains impurities 20 at a concentration of 60 ppm or more.

[0050] In one aspect, the extrudable material 30 containing impurities contains a polyolefin. The polyolefin can be polyethylene (PE), polypropylene (PP), or a mixture thereof. The extrudable material 30 containing impurities can be low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), polymethylpentene (PMP), polyisobutylene (PIB), polybutylene (PB), or a mixture thereof. The extrudable material 30 containing impurities can also be polyethylene terephthalate (PET), a polyamide (PA) such as copolyamide 6 / 66 (PA6 / 66), polylactic acid (PLA), or cellulose acetate (CA).

[0051] The extrudable material 30 containing impurities is, for example, derived from packaging materials. The extrudable material 30 containing impurities can be obtained from used packaging materials such as food packaging, pharmaceuticals, cosmetics, and oral care materials. In other examples, the extrudable material 30 containing impurities is recycled material, for example, recycled material obtained from a waste collection system, the so-called "yellow bag" ("gelber Sack" in the German packaging material collection system), a sorting center, or a paper mill. The recycled material may undergo steps such as sorting and separation by, for example, air classification or defiberization techniques, and / or washing steps using, for example, water or an alkaline solution, before extrusion of the recycled polymer from the extrudable material containing impurities.

[0052] As used herein, the term "low molecular impurity" means a molecule having a molecular weight of up to 500 g / mol. In one example, the low molecular impurity 20 has a molecular weight between 40 and 160 g / mol, and in a further example, the low molecular impurity 20 has a molecular weight between 60 and 130 g / mol.

[0053] In one aspect, the impurity 20 is one or more of a carboxylic acid, an aldehyde, a terpene, an aromatic, an olefin, an alkane, a nitrogen-based compound, a phosphorus-based compound, a sulfur-based compound, or a mixture thereof. In one example, the impurity 20 includes limonene, N-ethylformamide, N,N-dimethylguanidine, N-methoxymethyl-N-methylformamide, hexadecane, tetradecanoic acid, octadecane, n-hexadecanoic acid, eicosane, cis-13-octadecenoic acid, octadecanoic acid, docosane, tricosane, tetracosane, pentacosane, bis(2-ethylhexyl) phthalate, hexacosane, heptacosane, 1,3-benzenedicarboxylic acid, bis(2-ethylhexyl) ester, nonadecane, and mixtures thereof.

[0054] The term "non-solvent" includes mixtures that cannot dissolve the extrudable material 30 containing impurities. Examples of non-solvents 50 include water, mixtures of water, bases, esters, ethers, alkanes, alcohols, or ketones. Bases are, for example, ammonia or pyridine. Esters are, for example, ethyl acetate. Alcohols include methanol, ethanol, or isopropanol. Ketones are, for example, propanone.

[0055] The recycled polymer 100 has mechanical properties and sensory properties. The recycled polymer 100 has low odor properties.

[0056] By removing the impurities 20 from the extrudable material 30 containing impurities, a recycled polymer 100 having excellent mechanical properties such as toughness, elongation at break, and strength is obtained. This is due to the removal of the structural defects of the recycled polymer.

[0057] FIG. 5 shows a method for extruding a recycled polymer 100 from an extrudable material 30 containing impurities. In step 100, the extrudable material 30 containing impurities is fed through a hopper 15 into a housing 62 equipped with a mixing element 60 and melted using a heating device 80. By the rotation of the mixing element 60, the extrudable material 30 containing impurities in a molten state is advanced through the apparatus 10. The temperature within the housing 62 rises due to the work done on the extrudable material 30 containing impurities by the rotation of the mixing element 60 and the heating of the housing 62 by the heating element 80. For example, the temperature within the housing is between 130°C and 330°C, and in a further aspect, between 200°C and 230°C. For example, the temperature within the housing is between 110°C and 230°C, between 180°C and 230°C, between 250°C and 290°C, or between 250°C and 310°C. The increase in temperature causes an increase in pressure within the housing 62. The pressure within the housing 62 can be, for example, 2 to 300 bar (200 to 30000 kPa). The pressure within the housing 62 depends on the properties of the extrudable material 30 containing impurities, the properties of the non-solvent 50, the temperature within the housing 62, and the number of revolutions per minute of the mixing element 60. The pressure is selected such that the non-solvent 50 does not evaporate within the housing 62 but remains in a liquid state. The elevated temperature and high pressure within the apparatus can increase the rate of the method for extruding the recycled polymer 100 from the extrudable material 30 containing impurities. The term "high pressure" means that the pressure must be applied to prevent the evaporation of the non-solvent 50 in the injection zone at each processing temperature.

[0058] In step S110, the liquid non-solvent 50 is injected into the apparatus 10. The non-solvent 50 is injected into the apparatus 10 at a pressure such that the pressure inside the housing 62 of the apparatus 10 is higher than the vapor pressure of the non-solvent. At this pressure inside the apparatus 10, since the non-solvent 50 is in a liquid state inside the housing 62, the formation of foam inside the apparatus 10 is prevented, and a homogeneous mixing of the non-solvent 50 and the extrudable material 30 containing impurities becomes possible. In step 120, the extrudable material 30 containing the non-solvent 50 and impurities is mixed together substantially homogeneously by the mixing element 60 to form a dispersion 55 of the extrudable material 30 containing the non-solvent 50 and impurities. In one aspect of the present invention, the non-solvent 50 and the impurities 20 form an azeotropic mixture. Due to the homogeneous mixing of the extrudable material 30 containing the non-solvent 50 and impurities, the diffusion length of the homogeneous mixture is small, so that better absorption of the impurities 20 into the non-solvent 50 becomes possible, and thus it becomes easier to remove the impurities 20 from the extrudable material 30 containing the impurities.

[0059] With the discharge device 70, the pressure inside the housing 62 decreases, and the impurities 20 in the non-solvent 50 can move from the liquid state to the gaseous state. In step 130, the impurities 20 are discharged from the apparatus 10 in the gaseous state by the discharge device 70. In one aspect, the gaseous impurities 20 are discharged from the apparatus 10 into a vacuum. This (partial) vacuum is created, for example, by using a water-sealed vacuum pump. By discharging the gaseous impurities 20 into a vacuum, the impurities 20 can be extracted better from the extrudable material 30 containing the impurities into the non-solvent 50. The regenerated polymer 100 is produced and cooled in the water bath 110 through the material outlet 90 forcibly in step 150. The regenerated polymer 100 is cut into granules at the material outlet 90.

[0060] The term "azeotropic mixture" means a mixture in which the mole fraction of all components in the liquid state is equal to the mole fraction of all components in the gaseous state. The extrudable material 30 containing the impurity 20 is heated in the apparatus 10. By injecting the non-solvent 50, the formation of an azeotropic mixture between the impurity 20 and the non-solvent 50 becomes possible. The non-solvent 50 is injected into the apparatus 10 at a pressure of, for example, 3 to 90 bar (300 to 9000 kPa), and in one embodiment, at a pressure of 50 to 80 bar (5000 kPa to 8000 kPa). The temperature of the mixture within the apparatus 10 means that the impurity 20 is drawn into the non-solvent 50. The impurity 20 is then removed from the extrudable material 30 containing the impurity through the discharge device 70 in step 130.

[0061] In one example, the mixing element 60 has a low flight depth or a low screw pitch.

[0062] In one embodiment, the extrudable material 30 containing the impurity is passed through the melt filter 40 in step 105 before injecting the non-solvent 50 into the apparatus 10.

[0063] (Examples of processing conditions for extruding recycled polymers) The compositions listed below are merely examples of suitable formulations and do not limit the present invention (all in weight percent).

[0064] The concentrations of the following components of the extrudable material containing the impurity are measured by differential scanning calorimetry (DSC). The concentration of the impurity is measured by gas chromatography-mass spectrometry (GC-MS). The pressure within the injector is measured by a pressure gauge.

[0065] [Table 1]

[0066] [Table 2]

[0067]

Table 3

[0068]

Table 4

[0069]

Table 5

[0070]

Table 6

[0071] The examples listed below are merely examples of appropriate processing conditions for extruding a recycled polymer from an extrudable material containing impurities, and are not intended to limit the present invention. Examples 1 to 5 illustrate extrudable materials containing different impurities that can be processed to obtain a recycled polymer.

[0072] (Example 1) The extrudable material containing impurities has the shape of colored flakes derived from used consumer packaging materials. These colored flakes have, for example, an irregular geometric shape and a thickness of less than 50 μm. The concentration of impurities in the extrudable material containing the above impurities is 1.5%. The composition of the non-solvent injected into the apparatus is 43% water and 57% pyridine. The pressure in the injector is 21 bar (2100 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.1%.

[0073] (Example 2) The extrudable material containing impurities has the shape of colored flakes and is derived from used consumer packaging materials. The concentration of impurities in the extrudable material containing the above impurities is 1.2%. The composition of the non-solvent injected into the device is ethyl acetate. The pressure in the injector is 36 bar (3600 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.05%.

[0074] (Example 3) The extrudable material containing impurities has the shape of uncolored flakes and is derived from post-industrial recyclate. The concentration of impurities in the extrudable material containing the above impurities is 1.1%. The composition of the non-solvent injected into the device is isopropanol. The pressure in the injector is 28 bar (2800 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.01%.

[0075] (Example 4) The extrudable material containing impurities is derived from film scraps. The extrudable material containing impurities has, for example, a uniform geometric shape and a thickness exceeding 50 μm. The concentration of impurities in the extrudable material containing the above impurities is 1.5%. The composition of the non-solvent injected into the device is dioxane. The pressure in the injector is 72 bar (7200 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.1%.

[0076] (Example 5) The extrudable material containing impurities is derived from transfer film. The concentration of impurities in the extrudable material containing the above impurities is 1.2%. The composition of the non-solvent injected into the device is cyclohexane. The pressure in the injector is 27 bar (2700 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.1%.

[0077] (Example 6) The extrudable material containing impurities is derived from fiber recyclate. The concentration of impurities in the extrudable material containing the above impurities is 1.2%. The composition of the non-solvent injected into the apparatus is water. The pressure in the injector is 76 bar (7600 kPa). The concentration of impurities in the recycled polymer at the end of the treatment is less than 0.05%.

Explanation of Signs

[0078] 10 Apparatus 15 Hopper 20 Impurities 30 Extrudable material containing impurities 40 Melt filter 45 Injector 50 Non-solvent 55 Dispersion 57 Polymer melt 60 Mixing element 61 Screw device 62 Housing 63 Kneading block 64 Toothed disk 65 Single screw 66 Multi-screw 70 Discharge device 80 Heating device 90 Material outlet 100 Recycled polymer 110 Water bath

Claims

1. A method for extruding a recycled polymer (100) from an extrudeable material (30) containing impurities, The steps include: injecting a liquid non-solvent (50) into the apparatus (10) (S110), A mixing step (S120) comprising substantially homogeneously mixing the non-solvent (50) with the extrudeable material (30) containing the impurities, thereby forming a dispersion (55) of the non-solvent (50) and the extrudeable material (30) containing the impurities, A method comprising the step (S130) of discharging a gaseous impurity (20) from the apparatus (10).

2. The method according to claim 1, wherein the non-solvent (50) forms an azeotrope with the impurity (20).

3. The method according to claim 1, wherein the residual impurity concentration in the recycled polymer (100) is lower than 10 ppm.

4. The method according to claim 1, wherein the non-solvent (50) is selected from at least one of water, a mixture of water, a base, an ester, an alcohol, an ether, an alkane, or a ketone.

5. The method according to claim 4, wherein the base is at least one of ammonia or pyridine.

6. The method according to any one of claims 1 to 5, wherein the non-solvent (50) selected from alcohols is selected from methanol, ethanol, or isopropanol.

7. The method according to any one of claims 1 to 4, wherein the non-solvent (50) is a mixture of water and carbon dioxide.

8. The method according to any one of claims 1 to 5, wherein the impurity (20) has a maximum molecular weight of 500 g / mol.

9. The method according to any one of claims 1 to 5, wherein the impurity (20) is selected from one or more of carboxylic acids, aldehydes, terpenes, aromatics, olefins, alkanes, nitrogen compounds, phosphorus compounds, sulfur compounds, or mixtures thereof.

10. The method according to any one of claims 1 to 5, wherein the step of passing the extrudeable material (30) containing the impurities through a melt filter (40) (S105) is performed before the injection step (S110).

11. The method according to any one of claims 1 to 5, wherein the mixing step (S120) of the non-solvent (50) with the extrudeable material (30) containing the impurities is performed at a temperature between 110°C and 330°C.

12. The method according to any one of claims 1 to 5, wherein the mixing step (S120) of the non-solvent (50) with the extrudeable material (30) containing the impurities is performed at a pressure between 2 and 300 bar (200 and 30,000 kPa).

13. An apparatus (10) for removing impurities (20) from an extrudeable material (30) containing impurities, An injector (45) for injecting a liquid non-solvent (50) into an extrudeable material (30) containing the impurities, A mixing element (60) for substantially homogeneously mixing the non-solvent (50) with the extrudeable material (30) containing the impurities, The apparatus (10) comprises a discharge device (70) for discharging the impurity (20) in a gaseous state from the apparatus (10).

14. The apparatus (10) according to claim 13, wherein the non-solvent (50) is selected from at least one of water, a mixture of water, a base, an ester, an alcohol, an ether, an alkane, or a ketone.

15. The apparatus (10) according to claim 14, wherein the base is at least one of ammonia or pyridine.

16. The apparatus (10) according to any one of claims 13 to 15, wherein the non-solvent (50) selected from alcohols is selected from methanol, ethanol, or isopropanol.

17. The apparatus (10) according to any one of claims 13 to 15, wherein the impurity (20) has a maximum molecular weight of 500 g / mol.

18. The apparatus (10) according to any one of claims 13 to 15, wherein the impurity (20) is selected from one or more of carboxylic acids, aldehydes, terpenes, aromatics, olefins, alkanes, nitrogen compounds, phosphorus compounds, sulfur compounds, or mixtures thereof.

19. The apparatus (10) according to any one of claims 13 to 15, wherein the mixing element (60) comprises a screw device (61) within a housing (62).

20. The apparatus (10) according to any one of claims 13 to 15, wherein the mixing element (60) comprises either a single screw (65) or a multi-screw (66).

21. The apparatus (10) according to claim 19, wherein the screw device (61) comprises either a kneading block or a toothed disc.

22. A recycled polymer (100) comprising a polyolefin and impurities (20), wherein each of the impurities (20) is substantially homogeneously dispersed in the recycled polymer (100), and the concentration of each of the impurities (20) in the recycled polymer (100) is at most 10 ppm by weight.

23. The recycled polymer (100) according to claim 22, wherein the concentration of each of the impurities (20) in the recycled polymer (100) is a maximum of 5 ppm by weight.

24. The recycled polymer (100) according to claim 22, wherein the impurity (20) has a maximum molecular weight of 500 g / mol.

25. The recycled polymer (100) according to claim 22, wherein the impurity (20) is selected from one or more of carboxylic acids, aldehydes, terpenes, aromatics, olefins, alkanes, nitrogen compounds, phosphorus compounds, sulfur compounds, or mixtures thereof.

26. The recycled polymer (100) according to claim 22, wherein the polyolefin comprises polyethylene or polypropylene.

27. The recycled polymer (100) according to claim 22, wherein the recycled polymer (100) has low odor properties.

28. A method for using the recycled polymer (100) according to any one of claims 22 to 27, the method for use in a consumer package.

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