Removal of flame retardants from recycled plastics

Abstract

A method is disclosed for removing flame retardants from recycled plastics mate- rial. The method comprises obtaining recycled plastics material in a particulate form. The recycled plastics material in the particulate form is subjected to a first solvent extraction step with a first solution containing alkali metal hydroxide in an 5 amount of 1 to 10 wt-%, wherein the first solvent extraction step is performed at an absolute pressure of 1 to 6 bar, preferably above 1 bar, at a temperature of 90 to 160 oC, and above the glass transition temperature of the recycled plastics ma- terial, to extract flame retardants from the recycled plastics material to the first solution thereby reducing the flame retardants content of the recycled plastics ma-10 terial. The recycled plastics material having a reduced flame retardants content may then be recovered e.g. by filtering.

Description

[0001] REMOVAL OF FLAME RETARDANTS FROM RECYCLED PLASTICS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method of removing flame retardants from recycled plastics.

[0004] BACKGROUND ART

[0005] Polymers are widely used materials. Polymers are found especially in consumer products such as electronics and packaging materials. In Europe 25.8 million tonnes of plastics waste is generated annually. Less than 30 wt% of the plastics waste is collected for recycling. A significant share of the plastics waste is exported from the European Union to other countries for processing. Landfilling (30 wt%] and incineration (39 wt%] are the most common methods for treating plastics waste. Thus, a large amount of valuable material is lost from circulation.

[0006] Flame retardants are chemical compounds added to plastics in order to prevent or delay the ignition and burning of plastics and to slow down the spread of fire. Halogenated flame retardants may include materials such as bromine and chlorine compounds. Halogenated flame retardants release halogen gases when exposed to high temperatures, interfering with the combustion process, thus actively preventing the fire from spreading.

[0007] BRIEF DESCRIPTION

[0008] The scope of protection sought for various example embodiments is set out by the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments.

[0009] According to an aspect, there is provided a method for removing flame retardants from recycled plastics material, comprising obtaining recycled plastics material in a particulate form, subjecting the recycled plastics material in the particulate form to a first solvent extraction step with a first solution containing alkali metal hydroxide in an amount of 1 to 10 wt-%, wherein the first solvent extraction step is performed at an absolute pressure of 1 to 6 bar, at a temperature of 90 to 160 °C, and above the glass transition temperature of the recycled plastics material, to extract flame retardants from the recycled plastics material to the first solution thereby reducing the flame retardants content of the recycled plastics material, and recovering the recycled plastics material having a reduced flame retardants content.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which

[0012] Figure 1 illustrates a method according to an embodiment;

[0013] Figure 2 shows recycled ABS viscosity measurements results after solvent extraction compared to ABS reference sample;

[0014] Figure 3 shows recycled PP / PE viscosity measurements results after solvent extraction compared to PP / PE reference sample.

[0015] DETAILED DESCRIPTION OF EMBODIMENTS

[0016] The following embodiments are exemplifying. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment's), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

[0017] Exposure to halogenated flame retardants is associated with a wide range of adverse effects in humans and animals, including lowered IQ (intelligence quotient) in children, cancer, hormone disruption, and other serious health problems.

[0018] Currently, obstacles for efficient utilization of recycled plastics include safety concerns, low quality of the recycled material, and low recycling rates. The industry is also lacking standards for plastics recycling. A safety concern in plastics recycling is the presence of hazardous substances such as flame retardants including brominated flame retardants, BFR. Therefore, a challenge is to address the presence of hazardous substances such as brominated flame retardants, BFR, in the recycled feedstocks, and provide methods to effectively and safely debrominate the waste for new products. BFR content in plastics waste may be even up to 15 to 20 wt-%. BFRs are mostly hazardous substances, and their circulations is prohibited by legislation. To be able to circulate these challenging yet valuable waste plastics streams, effective debromination without destroying the polymer is desired.

[0019] It may be desired to decrease the bromine, antimony, and chlorine contents of recycled plastics below the legislative limit (EU) 1000 ppm. It is typically easier to decrease the antimony and chlorine levels from 1300 ppm to below 200 ppm. A more difficult task is to decrease the concentration of bromine compounds in the plastics waste to be below 1000 ppm or below, or 500 ppm or below.

[0020] Technical plastics typically have higher prices, and current recycling capacity is typically sold out. The movement of legislation towards mandatory recy- clate-content is increasing the demand for technical plastic recyclates. Polycar- bonate / acrylonitrile butadiene styrene (PC / ABS), acrylonitrile butadiene styrene (ABS), thermoplastic elastomers (TPE), ethylene propylene diene monomer (EPDM) rubber, polystyrene (PS), high impact polystyrene (Hl-PS), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) polymers cover about half of the European plastics demand (about 25 Mt out of 49 Mt). About half of the total ABS demand come from the waste from electrical and electronic equipment (WEEE) sector, this market was valued at 17,9 billion USD in 2020 with fast growing demand, being driven by the automobile companies’ need for lightweight materials. PP is the most used single polymer. 19.1 wt-% of European plastics demand is for PP, with a global market valued to be 78.3 billion USD in 2016. It also has the highest share for plastic materials in automotive and electrical and electronic equipment (EEE). Estimating only the WEEE brominated plastics (Hl-PS, ABS, PP, PC / ABS), the potential recyclable waste amount to more than 500 000 tons yearly.

[0021] An exemplary embodiment takes into account the presence of flame retardants, specifically the presence of brominated flame retardants, in the recycled plastics material, and provides a method for effective and safe removal of the flame retardants, specifically the brominated flame retardants, from the recycled plastics material, to enable the production of new products from the plastics material which has been treated by the method.

[0022] An exemplary embodiment utilizes a simple and effective extraction procedure using alkali metal hydroxide based solvents such as sodium hydroxide (NaOH) solution, straightforward mechanical separation techniques to separate the extracted plastic particles from the extraction media, and at the end simple washing cycles. The exemplary method for extracting BFRs from plastics waste may be easily scaled up into industrial quantities. Recycled plastics may also be referred to as plastics waste, waste plastics, and / or secondary plastics.

[0023] Exemplary plastics waste streams to be used as the recycled plastics in the method may include automotive interiors, heat insulations, large electrical appliances, such as refrigerators, and / or small electrical appliances. The product obtainable by the method, i.e. recycled plastics material having a reduced flame retardants content, may be utilized in the manufacture of automotive interiors, heat insulations, large electrical appliances, such as refrigerators, and / or small electrical appliances. An exemplary embodiment enables to obtain as product recycled plastics material, the mechanical properties of which are of sufficiently high quality to enable its reuse in automotive interiors, heat insulations, large electrical appliances, and / or small electrical appliances, etc.

[0024] An embodiment enables to efficiently debrominate technical plastic waste streams without destroying the polymer. In an embodiment, it is possible to avoid or at least minimize dissolving of the polymer during the solvent extraction. Dissolving the polymer may adversely affect the properties of the polymer, and therefore avoiding the dissolving during the extraction process is desired. This is based on selecting relatively mild processing conditions for the solvent extraction.

[0025] Figure 1 illustrates an exemplary method for removing flame retardants from recycled plastics material. Referring to Figure 1, the method may comprise obtaining recycled plastics material 101. If needed, the obtained recycled plastics material may be subjected to crushing or milling 102, so that the recycled plastics material is ground 102 into a particulate form. The obtained recycled plastics material in the particulate form 103 may have an average particle size in a range of 0.25 mm to 5 mm, preferably 0.5 mm to 2 mm. The obtained recycled plastics material in the particulate form 103 may then be subjected to a first solvent extraction step 104 with a first solution 121 containing alkali metal hydroxide, such as NaOH, in an amount of 1 to 10 wt-%, preferably 3 to 8 wt-%. The first solvent extraction step 104 may be performed at an absolute pressure of 1 to 6 bar, preferably above 1 bar, more preferably 1.5 to 6 bar, yet more preferably 3 to 5 bar, at a temperature of 90 to 160 °C, preferably 100 to 150 °C, and above the glass transition temperature of the recycled plastics material, to extract flame retardants from the recycled plastics material to the first solution thereby reducing the flame retardants content of the recycled plastics material. The recycled plastics material having a reduced flame retardants content 110 obtained by the first extraction step 104 may then be recovered e.g. by filtration 107. Instead of or in addition to filtration, centrifugation and / or decantation may be used for the recovery.

[0026] After the first solvent extraction step 104, the method may further comprise subjecting the recovered recycled plastics material having the reduced flame retardants content 110 to at least one further solvent extraction step 112 with a further solution 117 containing alkali metal hydroxide, and / or one or more Cl to C4 alcohol, such as isopropanol (1PA), in a total amount of 1 to 20 wt-%. The at least one further solvent extraction step 112 may be performed at an absolute pressure of 1 to 6 bar, preferably above 1 bar, more preferably 1.5 to 6 bar, yet more preferably 1.74 to 5.75 bar, at a temperature of 90 to 160 °C, and above the glass transition temperature of the recycled plastics material, to further extract flame retardants from the recycled plastics material to the further solution thereby further reducing the flame retardants content of the recycled plastics material. The recycled plastics material having a further reduced flame retardants content 120 obtained by the further solvent extraction step 112 may then be recovered e.g. by filtration 114. Instead of or in addition to filtration, centrifugation and / or decantation may be used for the recovery.

[0027] In an embodiment, the method may comprise a cooling step before or after step 107 and / or 108.

[0028] In an embodiment, the further solution 117 may comprise a mixture of alkali metal hydroxide solution with one or more Cl to C4 alcohol. The further solution 117 may contain alkali metal hydroxide, and / or one or more Cl to C4 alcohol, such as isopropanol (1PA), in a total amount of 1 to 20 wt-%.

[0029] In an embodiment, the further solution 117 may contain alkali metal hydroxide in an amount of 1 to 10 wt-%, preferably 3 to 8 wt-%, and the at least one further solvent extraction step 112 may be performed at a temperature of 100 to 160 °C preferably 100 to 150 °C. The further solution 117 may comprise alkali metal hydroxide solution and be essentially free of any Cl to C4 alcohol.

[0030] In an embodiment, the further solution 117 may contain one or more Cl to C4 alcohol in a total amount of 1 to 10 wt-%, preferably 3 to 8 wt-%, and the at least one further solvent extraction step 112 may be performed at a temperature of 90 to 100 °C. The further solution 117 may comprise a solution of one or more Cl to C4 alcohol and be essentially free of alkali metal hydroxide.

[0031] The first solution may be an aqueous solution of alkali metal hydrox- ide(s). The further solution may be an aqueous solution of alkali metal hydrox- ide(s) and / or Cl to C4 alcohol(s).

[0032] The method may comprise grinding 111 the recycled plastics material having the reduced flame retardants content 110 to an average particle size of 0.25 to 1 mm before the further solvent extraction step 112. The method may comprise washing, rinsing, and / or drying 111 the recycled plastics material having the reduced flame retardants content 110 before the further solvent extraction step 112. Water and / or ethanol, preferably water, may be used for the washing and / or rinsing 111, in order to remove solvent off the plastics.

[0033] In an embodiment, the first and further solvent extraction steps may be carried out in the same reaction vessel or separate reaction vessels.

[0034] The recycled plastics material may contain one or more of acrylonitrile butadiene styrene (ABS), polystyrene (PS), high impact polystyrene (Hl-PS), polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). The flame retardants may be halogenated flame retardants, such as brominated flame retardants and / or chlorinated flame retardants. Exemplary flame retardants to be removed by the method from the recycled plastics may include tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), decabromodiphenyl ether (decaBDE), decabromodiphenyl ethane, brominated carbonate oligomers (BCO), brominated epoxy oligomers (BEO), tetrabromophthalic anhydride, and / or chlorinated flame retardants. Recycled plastics may further include antimony trioxide, antimony pentoxide, and / or sodium antimonate as flame retardants.

[0035] The crushing or grinding 102, 111 of the recycled plastics may be carried out by using a grinder or a pulverizer to obtain the particulate form of the recycled plastics material.

[0036] Upon the brominated flame retardants content of the recycled plastics material being 5000 ppm or less, the method may comprise subjecting the recycled plastics material to the first solvent extraction step 104 and optionally to at least one further solvent extraction step 112. Upon the brominated flame retardants content of the recycled plastics material being above 5000 ppm, the method may comprise subjecting the recycled plastics material to the first solvent extraction step 104 and at least one further solvent extraction step 112.

[0037] The method may comprise extracting flame retardants from the recycled plastics material to the solution without dissolving the recycled plastics material.

[0038] The glass transition temperature of the recycled plastics material may depend on the type of the plastics. During the solvent extraction, the glass transition temperature of the plastics material may change due to the removal of sub- stance(s) from the material, which may lead to excessive plasticization of the plastics material. In an embodiment, the temperature used in the solvent extraction step(s) may be selected such that excessive plasticization of the recycled plastics material may be avoided or minimized during the solvent extraction.

[0039] The method may comprise recycling 115 at least part of the used first solution to the first solvent extraction step 104, via a solvent tank 106. The method may comprise recycling 115 at least part of the used further solution to the further solvent extraction step 112, via a solvent tank 116. This maybe performed e.g. after the filtration 107, 114 or centrifugation or decantation. In the solvent tank 106, 116, the recycled solvent 108, 115 may be made up by mixing fresh solvent into the used solvent.

[0040] Each solvent extraction step may be conducted for 1 to 2 hours, preferably about 1 hour. The alkali metal hydroxide may be at least one of sodium hydroxide (NaOH) and potassium hydroxide (KOH), preferably NaOH. The Cl to C4 alcohol maybe one or more of methanol, ethanol, 1-propanol, isopropanol, 1-buta- nol, 2-butanol, isobutanol, and tert-butanol, preferably at least one of ethanol and isopropanol, more preferably isopropanol (1PA).

[0041] The method may comprise obtaining as product recycled plastics material 110, 120 having a flame retardants content of 1000 ppm or less.

[0042] Used solvent 109, 119 removed from the process and containing flame retardants extracted from the plastics may be subjected to further treatment step(s) such as distillation and / or evaporation and recovered and reused, or further treated as hazardous waste. Recovered flame retardants extracted from the plastics may be industrially reusable. Incineration and / or use as landfill may be further processes used for lubricants recovered from the recycled plastics. Organic waste including a minor part of the plastics may be subjected to incineration.

[0043] In an embodiment, lubricant(s) (e.g. originating from ABS) may be separated by precipitating by acid from the used solvent 109, 119 after cooling and before the distillation and / or evaporation. The separated lubricant(s) may be reused for lubricant production. The lubricant may be or comprise EBS (ethylene- bis-stearamide), for example.

[0044] The method may include atleastone washing and / or at least one drying step after the first solvent extraction step and / or further solvent extraction step(s).

[0045] In an embodiment, the recycled plastics material contains recycled engineering plastics.

[0046] In an embodiment, upon brominated flame retardants content of the recycled plastics material being 5000 ppm or less, the method comprises subjecting the recycled plastics material to at least one solvent extraction step to obtain a brominated flame retardants content of the recycled plastics material of 1000 ppm or less.

[0047] In an embodiment, upon the brominated flame retardants content of the recycled plastics material being above 5000 ppm, the method comprises subjecting the recycled plastics material to two or more solvent extraction steps to obtain a brominated flame retardants content of the recycled plastics material of 1000 ppm or less.

[0048] In an embodiment, the method comprises decreasing the brominated flame retardants content of the recycled plastics material to be 1000 ppm or less, preferably 500 ppm or less.

[0049] In an embodiment, the recycled plastics may be ABS comprising TBBPA as brominated flame retardant, wherein the method comprises subjecting the recycled plastics material in the particulate form to the first solvent extraction step with alkali metal hydroxide, such as NaOH, as described above, to remove a desired amount of bromine compound(s) from the recycled plastics material.

[0050] In an embodiment, the recycled plastics may be PS comprising HBCD as brominated flame retardant, wherein the method comprises subjecting the recycled plastics material in the particulate form to the first solvent extraction step with alkali metal hydroxide, such as NaOH, and at least one further solvent extraction step with one or more Cl to C4 alcohol, such as 1PA, as described above, to remove a desired amount of bromine compound(s) from the recycled plastics material.

[0051] In an embodiment, the further solution in the second solvent extraction step may comprise aqueous solution of aromatic alcohol.

[0052] Example 1

[0053] 500 ml 1 M NaOH solution was used for solvent extraction of 24.13 g HIPS plastics particles ground with a 0.5 mm sieve. The brominated flame retardant in the plastics was TBBPA (tetrabromobisphenol A). The solvent extraction temperature was 150 °C, the extraction pressure was 3.9 to 4.0 bar overpressure (i.e. 4.9 to 5.0 bar absolute pressure), and the extraction time was 120 minutes. The starting concentration of Br was 22 751 ppm and starting concentration of Sb was 16 569 ppm. After the first solvent extraction, the concentration of Br was 1679 ppm, and the concentration of Sb was 17 179 ppm. The particles were ground before the second solvent extraction, such that in the second solvent extraction, the average particle size was 0.25 mm. In the second solvent extraction, the extraction temperature was 155 °C, the extraction pressure was 4.5 to 4.7 bar overpressure, and the extraction time was 120 minutes. After the second solvent extraction, the Br concentration was 1466 ppm, and the Sb concentration was 13 203 ppm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis. Example 2

[0054] 500 ml 1 M KOH solution was used for solvent extraction of 28.0 g HIPS plastics particles ground with a 0.5 mm sieve. The brominated flame retardant was TBBPA (tetrabromobisphenol A). The extraction temperature was 150 °C, the extraction pressure was 3.7 to 3.8 bar overpressure, and the extraction time was 120 minutes. The starting concentration of Br was 22 751 ppm, and the starting concentration of Sb was 16 569 ppm. After the first solvent extraction, the concentration of Br was 1631 ppm, and the concentration of Sb was 12 063 ppm. The particles were ground before the second solvent extraction. In the second solvent extraction, the average particle size was 0.25 mm. In the second solvent extraction, the extraction temperature was 155 °C, the extraction pressure was 4.5 to 4.7 bar overpressure, and the extraction time was 120 minutes. After the second solvent extraction, the Br concentration was 1184 ppm and the Sb concentration was 12 822 ppm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0055] Example 3

[0056] 500 ml 1 M NaOH solution was used for solvent extraction of 53.3 g recycled ABS plastics particles ground with a 0.25 mm sieve. The brominated flame retardant was TBBPA (tetrabromobisphenol A). The extraction temperature was 155 °C, the extraction pressure was 4.6 to 4.7 bar overpressure, and the extraction time was 120 minutes. The starting concentration was 60252 ppm for Br, 700 ppm for Cl, and 37 668 ppm for Sb. After the solvent extraction, the concentration of Br was 7417 ppm, the concentration of Cl was 1182 pp, and the concentration of Sb was 17 179 ppm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0057] Example 4

[0058] 500 ml 1 M NaOH and 50 ml isopropanol solution was used for solvent extraction of 46.4 g recycled ABS plastics particles ground with a 2.0 mm sieve. The brominated flame retardant was TBBPA (tetrabromobisphenol A). The extraction temperature was 140 °C, the extraction pressure was 4.8 bar overpressure, and the extraction time was 120 minutes. The starting concentration was 60 252 ppm for Br, 700 ppm for Cl, and 37 668 ppm for Sb. After the first solvent extraction, the concentration of Br was 11689 ppm, the concentration of Cl was 889 ppm, and the concentration of Sb was 19 351 ppm. After the first extraction, the sample was ground with a 1.0 mm sieve. The recycled solution from the first extraction was used for the second solvent extraction in which the extraction temperature was 135 °C, the extraction pressure was 4.4 to 4.8 bar overpressure, and the extraction time was 120 minutes. After the second solvent extraction, the concentration of Br was 8423 ppm, the concentration of Cl was 487 ppm, and the concentration of Sb was 16 552 ppm. After the second extraction, the sample was ground and sieved with a 0.5 mm sieve. The third extraction was carried out with the recycled solution from the second solvent extraction. The third extraction temperature was 135 °C, the third extraction pressure was 4,8 to 5,3 bar overpressure, and the third extraction time was 120 minutes. After the third extraction, the concentration of Br was 4261 ppm, the concentration of Cl was 763 ppm, and the concentration of Sb was 16 894 ppm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0059] Example 5 (comparative example)

[0060] 500 ml 1 M NaOH solution was used for the solvent extraction of 10.0 g HIPS plastics particles ground with a 3.0 mm sieve. The brominated flame retardant was TBBPA (tetrabromobisphenol A). The solvent extraction temperature was 95 °C, and the solvent extraction time was 1200 minutes (first extraction). The starting concentration of Br was 2067 ppm, and the starting concentration of Sb was 1487 ppm. After the first solvent extraction, the concentration of Br was 666 ppm, and the concentration of Sb was 1389 ppm. Then the sample was extracted (second extraction) with isopropanol solution for 720 minutes at 78 °C. After the second solvent extraction, the sample was ground with a 1.5 mm sieve, and subjected to the third solvent extraction with 1 M NaOH. The third solvent extraction temperature was 95 °C, and the third solvent extraction time was 1200 minutes. After that, the sample was washed with isopropanol for 720 minutes at 78 °C. After the third solvent extraction, the concentration of Br was 140 ppm, and the concentration of Sb was 1259 ppm. The pressure in the extractions was 1 atm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0061] Example 6 (comparative example)

[0062] 500 ml 1 M NaOH solution was used for solvent extraction of 10.0 g HIPS plastics particles ground with a 3.0 mm sieve. The brominated flame retardant was TBBPA (tetrabromobisphenol A). The extraction temperature was 95 °C, and the extraction time was 1200 minutes. The sample was washed with ethanol wash for 240 minutes at 60 °C. The starting concentration of Br was 20 136 ppm, and the starting concentration for Sb was 14213 ppm. After the first solvent extraction, the concentration of Br was 17 038 ppm, and the concentration of Sb was 1389 ppm. After the first solvent extraction, the sample was ground with a 1.5 mm sieve and extracted with 1 M NaOH. The second solvent extraction temperature was 95 °C, and the second solvent extraction time was 1200 minutes. The sample was washed with ethanol for 240 minutes at 60 °C. After the second solvent extraction, the concentration of Br was 1033 ppm, and the concentration of Sb was 13 172 ppm. The pressure in the extractions was 1 atm. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0063] Example 7

[0064] 500 ml isopropanol solution was used for the solvent extraction of 57.6 g Hl-PS plastics particles ground with a 0.5 mm sieve. The brominated flame retardant was DBDPE (decabromodiphenylethane). The extraction temperature was 95 °C, the extraction pressure was 1.3 to 1.4 bar overpressure, and the extraction time was 60 minutes. The starting concentration was 88 021 ppm for Br, 854 ppm for Cl, and 27 176 ppm for Sb. After the first solvent extraction, the concentration was 60 833 ppm for Br, 587 ppm for Cl, and 26927 ppm for Sb. After the first solvent extraction, the sample was ground with a 0.25 mm sieve and subjected to second solvent extraction with isopropanol. The second extraction temperature was 100 °C, the extraction pressure was 1.5 bar overpressure, and the second solvent extraction time was 120 minutes. After the second solvent extraction, the concentration was 42 811 ppm for Br, 726 ppm for Cl, and 27 650 ppm for Sb. The concentrations were obtained by Niton XRF (X-ray fluorescence) analysis.

[0065] Example 8

[0066] Figure 2 shows ABS basic property evaluation after solvent extraction compared to ABS reference sample. Figure 3 shows PP / PE basic property evaluation after solvent extraction compared to PP / PE reference sample. Measurement of ABS viscosity (Figure 2) and PP / PE viscosity (from WEEE) (Figure 3) before and after solvent extraction using capillary rheometer was carried out. Figures 2 and 3 show viscosity (Pa s) measured as a function of shear rate (1 / s). The measurement results revealed that both materials exhibit viscosities typical for injection moulding grade materials and shear-thinning behavior. No significant change was observed in melt viscosity after solvent extraction (taking into account the inherent heterogeneity of the plastic waste). Polymer integrity does not seem to be compromised by the solvent extraction.

[0067] Example 9

[0068] Table 1 shows GC-MS analysis results of NaOH extraction solution used in four times solvent extraction. The extraction temperature was 145 °C, and the extraction time was 120 minutes. Before the solution was analyzed, the solution was acidified with hydrochloric acid and extracted with dichloromethane. The main components detected in the analysis were tetrabromobisphenol-A and its degradation products bisphenol-A and tribromo bisphenol A. Thus NaOH selectively extracted bromine compounds (especially TBBPA) from the ABS plastics to the extraction solution.

[0069] Table 1 GC-MS analysis results of recycled NaOH solution used in solvent extraction of ABS plastics (2 M NaOH, 145 °C, ABS extraction)

[0070] Example 10

[0071] Table 2 shows GC-MS analysis results of isopropanol extraction solution used in three times solvent extraction. The extraction temperature was between 95 to 100 °C, the extraction pressure was 1.2 to 1.3 bar overpressure, and the extraction time was either 60 or 120 minutes. The main components detected in the analysis were tetrabromobisphenol-A and its degradation product tribromo bisphenol-A. Thus 1PA selectively extracted bromine compounds (especially TBBPA) from the ABS plastics to the extraction solution.

[0072] Table 2 GC-MS analysis results of 3 times recycled isopropanol solution used in solvent extraction of ABS plastics

[0073] Example 11

[0074] Tables 3 and 4 show a comparison of extraction methods for ABS samples, and Niton XRF (X-ray fluorescence) analysis results for the samples. The ex- traction pressure was atmospheric pressure. Table 3

[0075] Table 4 An XRF reference analysis for an ABS reference sample without extraction showed the following results: Br 1017 ppm, Cl 1314 ppm, Sb 304 ppm. As shown in Example 11, tables 3 and 4, clear analytical evidence of the superior washing power and selectivity towards BFRs was found for NaOH extraction (sample 67), compared to using Na acetate and / or urea as solvent (samples 64-66, 68-69, and reference sample).

[0076] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

CLAIMS1. A method for removing flame retardants from recycled plastics material, obtaining recycled plastics material in a particulate form; subjecting the recycled plastics material in the particulate form to a first solvent extraction step with a first solution containing alkali metal hydroxide in an amount of 1 to 10 wt-%, wherein the first solvent extraction step is performed at an absolute pressure of 1 to 6 bar, at a temperature of 90 to 160 °C, and above the glass transition temperature of the recycled plastics material, to extract flame retardants from the recycled plastics material to the first solution thereby reducing the flame retardants content of the recycled plastics material; and recovering the recycled plastics material having a reduced flame retardants content.

2. A method according to claim 1, wherein the first solution contains alkali metal hydroxide in an amount of 3 to 8 wt-%.

3. A method according to claim 1 or 2, wherein the first solvent extraction step is performed at a temperature of 100 to 150 °C.

4. A method according to any preceding claim, wherein the obtained recycled plastics material in the particulate form has an average particle size in a range of 0.25 mm to 5 mm, preferably 0.5 mm to 2 mm.

5. A method according to any preceding claim, comprising recovering the recycled plastics material having the reduced flame retardants content by filtration, decantation, or centrifugation.

6. A method according to any preceding claim, wherein after the first solvent extraction step, the method comprises subjecting the recovered recycled plastics material having the reduced flame retardants content to at least one further solvent extraction step with a further solution containing alkali metal hydroxide, and / or one or more Cl to C4 alcohol, in a total amount of 1 to 20 wt-%, wherein the at least one further solvent extraction step is performed at an absolute pressure of 1 to 6 bar, at a temperature of 90 to 160 °C, and above the glass transition temperature of the recycled plastics material, to further extract flame retardants from the recycled plastics material to the further solution thereby further reducing the flame retardants content of the recycled plastics material; and recovering the recycled plastics material having a further reduced flame retardants content.

7. A method according to claim 6, wherein the further solution contains alkali metal hydroxide in an amount of 1 to 10 wt-%, preferably 3 to 8 wt-%, wherein the at least one further solvent extraction step is performed at a temperature of 100 to 160 °C preferably 100 to 150 °C.

8. A method according to claim 6, wherein the further solution contains one or more Cl to C4 alcohol in an amount of 1 to 10 wt-%, preferably 3 to 8 wt-%, wherein the at least one further solvent extraction step is performed at a temperature of 90 to 100 °C.

9. A method according to claim 6 or 8, wherein the Cl to C4 alcohol is one or more of ethanol and isopropanol, preferably isopropanol.

10. A method according to claim 6, 7, 8 or 9, comprising recovering the recycled plastics material having the further reduced flame retardants content by filtration, decantation, or centrifugation.

11. A method according to claim 6, 7, 8, 9 or 10, comprising grinding the recycled plastics material having the reduced flame retardants content to an average particle size of 0.25 to 1 mm before the further solvent extraction step.

12. A method according to any preceding claim, wherein the recycled plastics material contains one or more of ABS, PS, Hl-PS, PE, PP, and PET.

13. A method according to any preceding claim, wherein the method comprises crushing recycled plastics by using a grinder or a pulverizer to obtain the particulate form of the recycled plastics material.

14. A method according to any preceding claim, wherein the flame retardants comprise brominated flame retardants.

15. A method according to any preceding claim, wherein upon the brominated flame retardants content of the recycled plastics material being 5000 ppm or less, the method comprises subjecting the recycled plastics material to the first solvent extraction step and optionally to at least one further solvent extraction step.

16. A method according to any preceding claim, wherein upon the brominated flame retardants content of the recycled plastics material being above 5000 ppm, the method comprises subjecting the recycled plastics material to the first solvent extraction step and at least one further solvent extraction step.

17. A method according to any preceding claim, wherein the method comprises extracting flame retardants from the recycled plastics material to the solution without dissolving the recycled plastics material.

18. A method according to any preceding claim, wherein the methodcomprises recycling at least part of the first solution, or further solution to the first or further solvent extraction step.

19. A method according to any preceding claim, wherein the method comprises conducting each solvent extraction step for 1 to 2 hours, preferably about 1 hour.

20. A method according to any preceding claim, wherein the alkali metal hydroxide is at least one of NaOH and KOH, preferably NaOH.

21. A method according to any preceding claim, wherein the first solvent extraction step is performed at an absolute pressure of above 1 bar, preferably 1.5 to 6 bar, more preferably 3 to 6 bar.

22. A method according to any preceding claim, wherein the further solvent extraction step is performed at an absolute pressure of above 1 bar, preferably 1.5 to 6 bar, more preferably 1.74 to 5.75 bar.

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