Method for recovering flame retardants from styrene polymer waste

Abstract

This disclosure relates to a method for separating flame retardants from styrene polymers in styrene polymer waste. The method comprises combining the styrene polymer waste with a solvent to obtain a soluble portion and an insoluble portion, and separating the soluble portion and the insoluble portion, such that the flame retardant is substantially in the soluble portion and the styrene polymer is substantially in the insoluble portion, or vice versa.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority from US 63 / 467,528, filed on 18 May 2023, which is incorporated in its entirety by reference.

[0002] field This disclosure relates to a method for separating flame retardants from styrene polymers in styrene polymer waste. This disclosure further relates to a method for recovering flame retardants from styrene polymer waste. [Background technology]

[0003] Used styrene polymer waste is routinely recycled to produce reusable recycled polymer materials. Much of the used styrene waste contains flame retardants with different chemical properties that are difficult to separate from the polymer material. Nevertheless, some of these flame retardants are valuable substances that can be reused or recycled, while others are harmful to consumer health and may be banned by the relevant authorities.

[0004] Therefore, it is necessary to develop a method for separating different flame retardants from styrene polymers in styrene polymer waste. [Overview of the project]

[0005] This specification demonstrates that flame retardants can be separated and recovered from styrene polymer waste by utilizing the differences in solubility between different flame retardants and styrene polymers in various solvents.

[0006] Therefore, in one embodiment, the present disclosure includes a method for recovering flame retardants from styrene polymer waste containing flame retardants and styrene polymers, the method including: Combining styrene polymer waste with a first solvent to obtain a soluble portion and an insoluble portion, and Separating soluble and insoluble parts; The flame retardant is substantially in the soluble portion, and the styrene polymer is substantially in the insoluble portion; or The flame retardant is substantially located in the insoluble portion, and the styrene polymer is substantially located in the soluble portion.

[0007] In some embodiments, the flame retardant is substantially in a soluble portion, and the styrene-based polymer is substantially in an insoluble portion.

[0008] In some embodiments, the method further includes recovering the flame retardant from the soluble portion by solvent removal. In some embodiments, solvent removal includes precipitation, crystallization, solvent evaporation, and combinations thereof.

[0009] In some embodiments, the method further includes combining the soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and recovering the precipitated flame retardant. In some embodiments, the recovery of the precipitated flame retardant is carried out by filtration, decantation, and / or centrifugation.

[0010] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of the first solvent after separation to obtain a washed portion and a washed insoluble portion.

[0011] In some embodiments, the method further includes combining a cleaning portion and a soluble portion to obtain a combined soluble portion.

[0012] In some embodiments, the method further includes combining the combined soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and recovering the precipitated or crystallized flame retardant. In some embodiments, the recovery of the precipitated flame retardant is carried out by filtration, decantation, and / or centrifugation.

[0013] In some embodiments, the flame retardant is selected from HBCD, PBDE, TBBPA, TBPC, octabromodiphenyl oxide (Octabrom), decabromodiphenyl oxide (DBDPO), and mixtures thereof.

[0014] In some embodiments, the first solvent is a non-solvent for styrene-based polymers, and the first solvent is C 5-8 Alkane, C 1-5 The solvent is selected from alkyl alcohols, alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), and mixtures thereof, or the first solvent is a mixture of a benzene-based solvent (e.g., selected from p-cymene, ethylbenzene, toluene, and mixtures thereof) and a polar aprotic solvent (e.g., selected from alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), ethers, N,N-dialkylamides (e.g., DMF), and mixtures thereof).

[0015] In some embodiments, the first solvent includes pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, methyl ethyl ketone, ethyl acetate, DMF, p-cymene, ethylbenzene, toluene, and mixtures thereof.

[0016] In some embodiments, the method further comprises washing the insoluble portion with one or more portions of a styrene-based polymer nonsolvent to obtain a washed insoluble portion. In some embodiments, the washing is carried out at a temperature above the glass transition state temperature (Tg) of the washed insoluble portion.

[0017] In some embodiments, the styrene-based polymer nonsolvent is C 5-8 Alkane, C 1-5 Alkyl alcohols and mixtures thereof are selected. In some embodiments, the styrene-based polymer nonsolvent is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0018] In some embodiments, the method further comprises drying the washed insoluble portion and recovering the styrenic polymer.

[0019] In some embodiments, the method further comprises: combining the insoluble portion with a second solvent to obtain a styrenic polymer mixture; heating the styrenic polymer mixture to a temperature sufficient to dissolve the styrenic polymer to obtain a styrenic polymer solution; combining the styrenic polymer solution with a styrenic polymer non-solvent to selectively precipitate the styrenic polymer; and recovering the precipitated styrenic polymer, optionally by filtration, decantation, and / or centrifugation; and optionally, washing the recovered styrenic polymer with one or more additional portions of the styrenic polymer non-solvent and drying the recovered styrenic polymer.

[0020] In some embodiments, the second solvent is selected from the first solvent as defined herein, cyclohexane, a mixture of acetone and a benzene-based solvent (e.g., p-cymene, toluene, ethylbenzene), and mixtures thereof.

[0021] In some embodiments, combining the insoluble portion with the second solvent is performed such that the styrenic polymer is present in the styrenic polymer mixture at about 5 wt% to about 30 wt%.

[0022] In some embodiments, the temperature is from about room temperature (25 °C) to about 100 °C.

[0023] In some embodiments, the flame retardant is substantially in the insoluble portion and the styrenic polymer is substantially in the soluble portion.

[0024] In some embodiments, the method further includes drying the insoluble portion and recovering the flame retardant.

[0025] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of a first solvent to obtain a washed portion and a washed insoluble portion.

[0026] In some embodiments, the method further includes drying the washed insoluble portion and recovering the flame retardant.

[0027] In some embodiments, the method further includes recovering the styrene-based polymer by solvent removal. In some embodiments, solvent removal includes solvent evaporation, precipitation, and / or crystallization.

[0028] In some embodiments, the first solvent is C 5-8 Alkane, C 1-5 The solvent is selected from alkyl alcohols and mixtures thereof. In some embodiments, the first solvent is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0029] In some embodiments, the flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

[0030] In some embodiments, the flame retardant is substantially in an insoluble portion, and the styrene polymer is substantially in a soluble portion, and the flame retardant comprises an inorganic flame retardant. In some embodiments, the inorganic flame retardant is selected from Sb2O3, ammonium halides, metal hydroxides (e.g., MgOH, aluminum trihydrate), Ca3(BO3)2, inorganic phosphates (e.g., ammonium phosphate), and mixtures thereof.

[0031] In some embodiments, the method further comprises combining the soluble and insoluble portions with a third solvent before separating the soluble and insoluble portions to obtain a microgel in which the soluble portion contains a portion of the styrene polymer; and The soluble and insoluble portions are separated by centrifugation. As a result, the styrene-based polymer microgel exists as a suspension in the soluble portion and as a pellet in the insoluble portion.

[0032] In some embodiments, the third solvent can swell the styrene-based polymer or form a gel with the styrene-based polymer.

[0033] In some embodiments, the third solvent is selected from p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

[0034] In some embodiments, the microgel contains about 15 wt% to about 25 wt% of a styrene-based polymer. In some embodiments, the styrene-based polymer is selected from HIPS, ABS, and mixtures thereof. Both HIPS and ABS can be recognized as containing a polybutadiene component (e.g., an elastomer domain of polybutadiene). In some embodiments, the microgel contains the polybutadiene component of the styrene-based polymer.

[0035] In some embodiments, the method further includes recovering the pellets, recovering the flame retardant, and optionally washing the pellets with one or more further portions of the first solvent.

[0036] In some embodiments, the inorganic flame retardant includes Sb2O3.

[0037] In some embodiments, the styrene polymer waste further comprises an inorganic pigment, optionally the inorganic pigment comprising TiO2, the inorganic pigment being recovered together with an inorganic flame retardant, optionally the method further comprising separating Sb2O3 from TiO2, optionally the separation being carried out by selectively solubilizing Sb2O3 in a basic medium, optionally the basic medium comprising an aqueous hydroxide solution (e.g., KOH, NaOH, LiOH).

[0038] In some embodiments, the flame retardant further comprises an organic flame retardant.

[0039] In some embodiments, the organic flame retardant is selected from PBDE, TBBPA, TBPC, octabromodiphenyl oxide (Octabrom), decabromodiphenyl oxide (DBDPO), and mixtures thereof.

[0040] In some embodiments, the organic flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

[0041] In some embodiments, the method further includes separating the inorganic flame retardant from the organic flame retardant.

[0042] In some embodiments, the method further includes purifying the recovered flame retardant.

[0043] In some embodiments, the styrene polymer is selected from ABS, HIPS, atactic polystyrene (PS), SAN, SBS, syndiotactic PS, isotactic PS, styrene-methyl methacrylate (SMMA), methyl methacrylate-acrylonitrile-butadiene-styrene (MABS), methyl methacrylate-butadiene-styrene (MBS), and mixtures thereof.

[0044] In another aspect, the disclosure includes a method for recovering a flame retardant from polymer waste, wherein the polymer comprises a flame retardant and a polymer, and the method includes: The polymer waste is combined with a first solvent to obtain a soluble portion and an insoluble portion, and Separating soluble and insoluble parts; The flame retardant is substantially in the soluble portion, and the polymer is substantially in the insoluble portion; or, The flame retardant is substantially in the insoluble portion, and the polymer is substantially in the soluble portion.

[0045] Embodiments of this disclosure will be described in more detail below with reference to the attached drawings. [Brief explanation of the drawing]

[0046] [Figure 1] A flowchart illustrating an exemplary method 100 of this disclosure is shown. [Figure 2] A flowchart illustrating an exemplary method 200 of this disclosure is shown. [Figure 3] A flowchart illustrating an exemplary method 300 of this disclosure is shown, in which an insoluble flame retardant is recovered in a first solvent, and in addition, an optional soluble flame retardant may be present in the styrene polymer waste.

[0047] Other features and advantages of this disclosure will become apparent from the detailed description below. However, it should be understood that the detailed description and specific examples illustrate embodiments of this disclosure, but are provided only as examples, and the claims should not be limited by these embodiments, but rather given the broadest interpretation consistent with the overall description. [Modes for carrying out the invention]

[0048] I. Definition Unless otherwise noted, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present disclosure described herein, as they are preferred to be understood by those skilled in the art.

[0049] The term "and / or" in this specification means that the enumerated items exist or are used individually or in combination. In effect, the term means that "at least one" or "one or more" of the enumerated items are used or exist.

[0050] As used in this disclosure, the singular forms “a, an” and “the” include plural references unless otherwise clearly indicated in the context. For example, “an embodiment containing a compound” should be understood to present a certain aspect having one compound or two or more additional compounds.

[0051] In embodiments comprising an “additional” or “secondary” component, for example, an additional or second solvent, the second component used herein is chemically different from the other or first components. The “third” component is different from the other, first, and second components, and the further listed or “additional” components are similarly different.

[0052] As used in this disclosure and claims, the words “comprising” (and any form of “comprising,” e.g., “comprise” and “comprises”), “having” (and any form of “having,” e.g., “have” and “has”), “including” (and any form of “including,” e.g., “include” and “includes”), or “containing” (and any form of “containing,” e.g., “contain” and “contains”) are inclusive, unrestrictive, and do not exclude additional, undescribed elements or process steps.

[0053] The term "composed" and its derivatives are intended in this specification to be closed terms that identify the presence of described features, elements, components, groups, integers, and / or steps, and exclude the presence of other undescribed features, elements, components, groups, integers, and / or steps.

[0054] The term “essentially composed of” is intended herein to identify the features, elements, components, groups, integers, and / or steps described, as well as the presence of anything that does not substantially affect the basic and novel properties of these features, elements, components, groups, integers, and / or steps.

[0055] This document lists many chemical terms and abbreviations used by those skilled in the art. Nevertheless, definitions of selected terms are provided to ensure clarity and consistency.

[0056] The terms “about,” “substantially,” and “approximately” in this specification mean a reasonable amount of deviation from the modified term such that the final result does not change materially. Terms of these degrees should be interpreted as including a deviation of at least ±5% of the modified term, unless the deviation does not negate the meaning of the modified term or is otherwise suggested by the context to a person skilled in the art.

[0057] The term "styrene-based polymer" as used herein means a polymer, for example, a homopolymer or copolymer, wherein at least one monomer is a styrene-based monomer or a vinyl aromatic monomer. For example, styrene-based polymers include homopolymers of styrene (i.e., polystyrene) and copolymers of styrene with one or more polymerizable monomers. For example, styrene-based polymers also include graft polymers, for example, homopolymers or copolymers containing at least one styrene-based monomer or a vinyl aromatic monomer grafted with a non-styrene-based polymer, or homopolymers or copolymers containing at least one styrene-based monomer or a vinyl aromatic monomer grafted with one or more other homopolymers or copolymers containing at least one styrene-based monomer or a vinyl aromatic monomer. Copolymers can be block copolymers.

[0058] The term "styrene polymer waste" as used herein means waste material comprising at least one styrene polymer and a flame retardant as described herein.

[0059] The term “non-solvent” for a particular substance, as used herein, means a compound or mixture of compounds in which the substance is substantially insoluble. For example, a styrene polymer non-solvent refers to a compound or mixture of compounds in which the styrene polymer is substantially insoluble. For example, a flame retardant non-solvent refers to a compound or mixture of compounds in which one or more types of flame retardants are not substantially insoluble.

[0060] II. Method of Disclosure This disclosure relates to a method for recovering flame retardants from styrene polymer waste.

[0061] Figure 1 is shown as Method Example 100 of the present disclosure. In step 102, the styrene polymer waste to be recycled is combined with the first solvent. The styrene polymer waste is partially solubilized. In step 104, the soluble and insoluble portions are separated. The flame retardant is present in either the soluble or insoluble portion and can therefore be recovered.

[0062] Figure 2 illustrates an example of the method 200 of this disclosure. In step 202, the styrene polymer waste to be recycled is combined with a first solvent. The styrene polymer waste is partially solubilized. In step 204, the soluble and insoluble portions are separated. Then, in step 206, it is determined whether the flame retardant is present in the soluble portion or also in the insoluble portion. The styrene polymer is present in the other portion.

[0063] If the flame retardant is in a soluble portion and the styrene polymer is in an insoluble portion, the method proceeds to step 208, where the flame retardant is recovered from the soluble portion by solvent removal. For example, solvent removal can be achieved by means known in the art, for example, evaporation, selective precipitation, and crystallization, but not limited to these. Optionally, the insoluble portion can be washed with a further portion of the first solvent, as shown in step 212, to further extract any residual flame retardant in the insoluble portion. To facilitate the extraction of residual flame retardant, the insoluble portion can be combined with a certain amount of styrene polymer solvent to swell the styrene polymer into a gel or paste. The washing in step 212 can then be carried out at a temperature higher than the glass transition temperature (Tg) of the polymer gel or paste, maintaining greater flexibility of the gel / paste and facilitating the extraction of residual flame retardant.

[0064] The washing portion from step 212 can be combined with the soluble portion in step 214. The flame retardant can be extracted from the combined soluble portion by solvent removal as described herein.

[0065] If it is determined that the flame retardant is in the insoluble portion and the styrene polymer is in the soluble portion, the method proceeds to step 210, where the insoluble portion is dried and the flame retardant is recovered. Optionally, in step 222, the insoluble portion can be further washed with a further portion of the first solvent to remove any residual polymer. The soluble portion containing the styrene polymer may be used in an optional step 220, where the styrene polymer is recovered by solvent removal as described herein.

[0066] As shown in step 218, as soon as the flame retardant is removed in steps 208 and 210, the recovered flame retardant can be purified by means known in the art, for example, by recrystallization and / or column chromatography.

[0067] Figure 3 illustrates an example of the method 300 of the present disclosure, in which the flame retardant is present in the soluble portion and the styrene polymer is present in the insoluble portion. In step 302, the styrene polymer waste to be recycled is combined with a first solvent. The styrene polymer waste is partially solubilized. Optionally, before separating the soluble and insoluble portions (304), the styrene polymer non-solvent is combined with the mixture of the soluble and insoluble portions in step 308 to obtain a microgel containing part of the styrene polymer, with the remainder of the styrene polymer in the soluble portion. The mixture obtained from step 308 can optionally be centrifuged in step 310, and the microgel remains as a suspension in the soluble portion containing the styrene polymer. The insoluble flame retardant settles at the bottom as pellets after centrifugation. The mixture is then separated as shown in step 304.

[0068] As shown in step 312, the insoluble portion containing the flame retardant can optionally be washed with a further portion of the first solvent to extract the polymer.

[0069] The soluble mixture obtained from step 304 can be used to determine whether it contains further soluble flame retardants. If so, the soluble flame retardants or polymers can be selectively extracted, for example, by selectively precipitating either the flame retardant or the polymer (step 318). Otherwise, the styrene-based polymer can optionally be recovered by solvent removal in step 316.

[0070] In one embodiment, the disclosure includes a method for recovering a flame retardant from styrene polymer waste, wherein the styrene polymer comprises a flame retardant and the styrene polymer, and the method includes: Combining styrene polymer waste with a first solvent to obtain a soluble portion and an insoluble portion, and Separating soluble and insoluble parts; The flame retardant is substantially in the soluble portion, and the styrene polymer is substantially in the insoluble portion; or The flame retardant is substantially located in the insoluble portion, and the styrene polymer is substantially located in the soluble portion.

[0071] In some embodiments, the flame retardant is substantially in a soluble portion, and the styrene-based polymer is substantially in an insoluble portion.

[0072] In some embodiments, the method further includes recovering the flame retardant from the soluble portion by solvent removal. In some embodiments, solvent removal includes precipitation, crystallization, solvent evaporation, and combinations thereof.

[0073] In some embodiments, the method further includes combining the soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and recovering the precipitated flame retardant. In some embodiments, the recovery of the precipitated flame retardant is carried out by filtration, decantation, and / or centrifugation.

[0074] In some embodiments, the method further comprises washing the insoluble portion after separation with one or more additional portions of the first solvent to obtain a washed portion and a washed insoluble portion.

[0075] In some embodiments, the method further includes combining a cleaning portion and a soluble portion to obtain a combined soluble portion.

[0076] In some embodiments, the method further includes combining the combined soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and recovering the precipitated or crystallized flame retardant. In some embodiments, the recovery of the precipitated or crystallized flame retardant is carried out by filtration, decantation, and / or centrifugation.

[0077] In some embodiments, the flame retardant is selected from HBCD, PBDE, TBBPA, TBPC, octabromodiphenyl oxide (Octabrom), decabromodiphenyl oxide (DBDPO), and mixtures thereof.

[0078] In some embodiments, the first solvent is a non-solvent for styrene-based polymers, and the first solvent is C 5-8 Alkane, C 1-5 The solvent is selected from alkyl alcohols, alkyl esters, alkyl ketones, and mixtures thereof, or the first solvent is a mixture of benzene-based solvents (e.g., selected from p-cymene, ethylbenzene, toluene, and mixtures thereof) and polar aprotic solvents (e.g., selected from alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), ethers, N,N-dialkylamides (e.g., DMF), and mixtures thereof).

[0079] In some embodiments, the first solvent includes pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, methyl ethyl ketone, ethyl acetate, DMF, ethyl acetate, p-cymene, ethylbenzene, toluene, and mixtures thereof.

[0080] In some embodiments, the method further includes washing the insoluble portion with one or more portions of a styrenic polymer non-solvent to obtain a washed insoluble portion. In some embodiments, the washing is performed at a temperature above the glass transition temperature (Tg) of the washed insoluble portion.

[0081] In some embodiments, the styrenic polymer non-solvent is C 5-8 alkane, C 1-5 alkyl alcohol, and mixtures thereof. In some embodiments, the styrenic polymer non-solvent is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0082] In some embodiments, the method further includes drying the washed insoluble portion to recover the styrenic polymer.

[0083] In some embodiments, the method further includes: combining the insoluble portion with a second solvent to obtain a styrenic polymer mixture; heating the styrenic polymer mixture to a temperature sufficient to dissolve the styrenic polymer to obtain a styrenic polymer solution; combining the styrenic polymer solution with a styrenic polymer non-solvent to selectively precipitate the styrenic polymer; and recovering the precipitated styrenic polymer, optionally by filtration, decantation, and / or centrifugation; and Optionally, wash the recovered styrene polymer with one or more additional portions of a styrene polymer non-solvent and dry the recovered styrene polymer.

[0084] In some embodiments, the second solvent is selected from the first solvent as defined herein, cyclohexane, mixtures of acetone and benzene-based solvents (e.g., p-cymene, toluene, ethylbenzene), and mixtures thereof.

[0085] In some embodiments, the combination of the insoluble portion and the second solvent is carried out such that the styrene polymer is present in the styrene polymer mixture at an amount of about 5 wt% to about 30 wt%.

[0086] In some embodiments, the temperature is approximately room temperature (25°C) to approximately 100°C.

[0087] In some embodiments, the flame retardant is substantially in an insoluble portion, and the styrene-based polymer is substantially in a soluble portion.

[0088] In some embodiments, the method further includes drying the insoluble portion and recovering the flame retardant.

[0089] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of a first solvent to obtain a washed portion and a washed insoluble portion.

[0090] In some embodiments, the method further includes drying the washed insoluble portion and recovering the flame retardant.

[0091] In some embodiments, the method further includes recovering the styrene-based polymer by solvent removal. In some embodiments, solvent removal includes solvent evaporation, precipitation, and / or crystallization.

[0092] In some embodiments, the first solvent is C 5-8 Alkane, C 1-5The solvent is selected from alkyl alcohols and mixtures thereof. In some embodiments, the first solvent is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0093] In some embodiments, the flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

[0094] In some embodiments, the flame retardant is substantially in an insoluble portion, and the styrene polymer is substantially in a soluble portion, and the flame retardant comprises an inorganic flame retardant. In some embodiments, the inorganic flame retardant is selected from Sb2O3, ammonium halides, metal hydroxides (e.g., MgOH, aluminum trihydrate), Ca3(BO3)2, inorganic nitrates (e.g., ammonium nitrate), inorganic phosphates (e.g., ammonium phosphate), inorganic phosphonates, and mixtures thereof.

[0095] Those skilled in the art will recognize that inorganic flame retardants, particularly Sb2O3, are used as synergists with organic flame retardants. When used in combination, the amount of organic flame retardant can be reduced due to the presence of the synergist. Therefore, the method of this disclosure enables the separation and recovery of synergists from styrene polymer waste.

[0096] In some embodiments, the method further comprises combining the soluble and insoluble portions with a third solvent before separating the soluble and insoluble portions to obtain a microgel in which the soluble portion contains a portion of the styrene polymer; and The soluble and insoluble portions are separated by centrifugation. As a result, the styrene-based polymer microgel exists as a suspension in the soluble portion and as a pellet in the insoluble portion.

[0097] In some embodiments, a third solvent can swell the styrene polymer or form a gel with the styrene polymer. Such a solvent can swell a portion of the styrene polymer or some of its components into a microgel, which can be observed to have a density similar to that of the soluble portion. Thus, centrifugation of the mixture leaves the microgel in the suspension, allowing the insoluble portion to settle.

[0098] In some embodiments, the third solvent is selected from p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

[0099] In some embodiments, the microgel contains about 15 wt% to about 25 wt% of a styrene-based polymer. In some embodiments, the styrene-based polymer is selected from HIPS, ABS, and mixtures thereof. Both HIPS and ABS can be recognized as containing a polybutadiene component (e.g., an elastomer domain of polybutadiene). In some embodiments, the microgel contains the polybutadiene component of the styrene-based polymer.

[0100] In some embodiments, the method further includes recovering the pellets, recovering the flame retardant, and optionally washing the pellets with one or more further portions of the first solvent.

[0101] In some embodiments, the inorganic flame retardant includes Sb2O3.

[0102] In some embodiments, the styrene polymer waste further comprises an inorganic pigment, optionally the inorganic pigment comprising TiO2, the inorganic pigment being recovered together with an inorganic flame retardant, and optionally the method further comprising separating Sb2O3 from TiO2, optionally the separation being carried out by selectively solubilizing Sb2O3 in a basic medium, optionally the basic medium comprising an aqueous hydroxide solution (e.g., KOH, NaOH, LiOH).

[0103] In some embodiments, the flame retardant further comprises an organic flame retardant.

[0104] In some embodiments, the organic flame retardant is selected from PBDE, TBBPA, TBPC, and mixtures thereof.

[0105] In some embodiments, the organic flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

[0106] In some embodiments, the method further includes separating the inorganic flame retardant from the organic flame retardant.

[0107] In some embodiments, the method further includes purifying the recovered flame retardant.

[0108] In some embodiments, the styrene polymer is selected from ABS, HIPS, atactic polystyrene (PS), SAN, SBS, syndiotactic PS, isotactic PS, styrene-methyl methacrylate (SMMA), methyl methacrylate-acrylonitrile-butadiene-styrene (MABS), methyl methacrylate-butadiene-styrene (MBS), and mixtures thereof.

[0109] In some embodiments, styrene-based polymers are derived from styrene-based monomers or vinyl aromatic monomers copolymerized with one or more polymerizable monomers. For example, one or more polymerizable monomers can be unsaturated nitriles. Examples of unsaturated nitriles include, but are not limited to, acrylonitrile, methacrylonitrile, ethacrylonitrile, fumaronitrile, and mixtures thereof.

[0110] In some embodiments, styrene polymers can be crosslinked and / or grafted with one or more other polymers. Examples of these other polymers include polymerized conjugated alkenes. For example, conjugated alkenes include dienes, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2-methyl-1,3-pentadiene, and other such dienes, and mixtures thereof. In some embodiments, the conjugated alkene is 1,3-butadiene, isoprene, or a mixture thereof.

[0111] In some embodiments, the styrene polymer is selected from acrylonitrile-butadiene styrene (ABS), high-impact polystyrene (HIPS), styrene-acrylonitrile copolymer (SAN), styrene-butadiene styrene copolymer (SBS), and mixtures thereof.

[0112] In some cases, those skilled in the art will recognize that, in order to soften a gel formed by a styrene polymer swollen with a solvent, it may be useful to select a styrene polymer non-solvent having a boiling point approximately at or slightly above the glass transition temperature (Tg). For example, it may be desirable to facilitate the removal of soluble flame retardants by heating a gel or microgel containing a styrene polymer and a styrene polymer non-solvent to near the Tg of the styrene polymer gel or microgel, and then washing the gel or microgel with a further portion of the styrene polymer non-solvent at or near the boiling point of the non-solvent.

[0113] In some embodiments, the styrene-based polymer nonsolvent is C 5-8 Alkane, C 1-6 The solvent is selected from alkyl alcohols and mixtures thereof. It can be recognized that a suitable nonsolvent can be selected for the particular styrene-based polymer in question by means known in the art.

[0114] In some embodiments, the flame retardant nonsolvent is C5-8 Alkane, C 1-6 Alkyl alcohols and mixtures thereof are selected. It can be recognized that suitable nonsolvents can be selected for a particular flame retardant of interest by means known in the art. For example, if the flame retardant properties present in styrene polymer waste are known or determined, a specific nonsolvent can be selected accordingly.

[0115] In some embodiments, recovered flame retardants are reused in the manufacture of polymer materials. For example, the polymer material may include styrene-based polymers or non-styrene-based polymers. For example, the polymer material may include thermoplastic and / or thermosetting plastics. For example, the polymer material may include polyolefins (e.g., polyethylene, polypropylene), polycarbonates, epoxy, polyesters, polyamides, or mixtures or copolymers thereof.

[0116] In some embodiments, the styrene polymer waste further comprises inorganic pigments, such as TiO2. The inorganic pigments have insolubility similar to that of the inorganic flame retardants described herein. As such, the inorganic pigments can be recovered from the styrene polymer waste together with the inorganic flame retardants. As soon as the inorganic pigments and inorganic flame retardants are recovered, they can be separated using methods known in the art. For example, some inorganic compounds can be selectively solubilized or precipitated in an acidic or basic medium. Thus, certain compounds can be selectively solubilized by adding an acid or base to the recovered inorganic compounds. For example, Sb2O3 is known to be soluble in basic media, while TiO2 is not. A mixture of Sb2O3 and TiO2 recovered from the styrene polymer waste can be separated from each other by selectively solubilizing the Sb2O3 in a basic medium (e.g., by adding an aqueous hydroxide solution) and filtering out the solid TiO2. Both the inorganic pigments and inorganic flame retardants are reusable, for example, in the manufacture of other polymer materials.

[0117] In some embodiments, the purification of the recovered flame retardant includes selective precipitation, recrystallization, column chromatography (e.g., silica column), or a combination thereof.

[0118] Examples The following non-limiting embodiments are illustrative of the present disclosure.

[0119] General method All solvents were high-purity chromatography-grade and purchased from Sigma Aldrich. Flame retardants were also purchased from Sigma Aldrich or a specialized flame retardant provider. The X-ray fluorescence spectrophotometer used was a Bruker Titan S1.

[0120] Example 1 Solubility test of flame retardants in different solvents The solubility of many common flame retardants was tested in various solvents. A 2 wt% solution of each flame retardant was prepared in different solvents at room temperature. The solubility results are shown in Table 1. [Table 1]

[0121] Flame retardants that are not completely soluble in a particular solvent (e.g., partially or mostly soluble) are expected to be substantially solubilized by increasing the temperature of the solution.

[0122] Example 2: Recovery of brominated and inorganic flame retardants from ABS Model styrene-based polymer waste materials were prepared using ABS pellets and different brominated flame retardants. Mixture A was prepared using 10 g of ABS pellets and 1 g of 3,3',5,5'-tetrabromobisphenol A (TBBPA) in 90 g of ethyl acetate. Mixture B was prepared using 10 g of ABS pellets and 1 g of NN-ethylene-bis(tetrabromophthalimide) in 90 g of ethyl acetate.

[0123] Both mixtures were vigorously stirred at room temperature for 5 hours. The resulting mixtures were centrifuged at 8500 rpm for 20 minutes. The bromine content of the supernatant was evaluated using X-ray fluorescence. The results are shown in Table 2. [Table 2]

[0124] As shown in Table 2, NN-ethylene-bis(tetrabromophthalimide) did not dissolve in ethyl acetate and was removed by centrifugation of the mixture.

[0125] Analysis of the centrifugal residue from mixture B reveals the presence of some microgels containing NN-ethylene-bis(tetrabromophthalimide) and polybutadiene (PBu). This residue is washed twice with 50 g of ethyl acetate to further remove the soluble ABS portion. The washed residue is dried at 100°C for 2 hours. The dried residue contains NN-ethylene-bis(tetrabromophthalimide), which is reusable.

[0126] Alternatively, the residue from mixture B containing a copolymer of NN-ethylene-bis(tetrabromophthalimide) and PBu and / or PBu microgels is dispersed in 100 g of toluene or a copolymer of a good PbU and / or PBu swelling agent. The resulting mixture is heated to 60°C with stirring for 5 hours. The resulting mixture is centrifuged at 3000 rpm for 5 minutes. The microgels containing the PBu portion remain in the supernatant suspension, while the NN-ethylene-bis(tetrabromophthalimide) settles at the bottom as a pellet. The polymers PBu and NN-ethylene-bis(tetrabromophthalimide) are separated and can be reused, respectively.

[0127] As shown in Table 2, TBBPA was soluble in ethyl acetate and remained in the supernatant of mixture A after centrifugation, and ABS was also soluble.

[0128] The supernatant of mixture A is combined with 60 g of a styrene-based polymer non-solvent (e.g., heptane or methanol) to form a paste. The combination is carried out at room temperature or a suitable temperature, so that the polymer paste is maintained above its glass transition temperature (Tg). The supernatant solvent is recovered as fraction 1. The paste is then washed twice with a mixture of ethyl acetate and a non-solvent (e.g., heptane or methanol) at a temperature and solvent ratio that maintains the polymer in a paste form above its Tg. Each washed portion is retained as fraction 2 and fraction 3, respectively. Fractions 1-3 are combined, the solvent is evaporated, and TBBPA is recovered. The dried TBBPA is further purified by dissolving any remaining trace amounts of polymer in a solvent for styrene-based polymers, e.g., p-cymene, or a mixture of a styrene-based polymer solvent and a styrene-based polymer non-solvent (e.g., a mixture of p-cymene and heptane), in which case TBBPA is not soluble. The remaining polymer in the recovered TBBPA is soluble in the solvent. The solution is filtered to remove the soluble portion containing polymers (e.g., ABS, SAN, and small amounts of chain-like impurities). The residue is washed with a fresh portion of the same solvent and dried to obtain purified TBBPA. The purified TBBPA can be further purified, for example, by recrystallization.

[0129] Example 3: Recovery of inorganic flame retardant from used HIPS 30 g of used HIPS waste was dissolved in p-cymene to produce a solution containing 15 wt% of the HIPS waste. Approximately 10 wt% methanol was added to this solution. The resulting mixture was centrifuged at 8500 rpm for 20 minutes. The supernatant was collected. 340 g of heptane was added to the supernatant to precipitate the polymer content. The precipitate was removed as a paste and washed at a temperature higher than its Tg. The content of various inorganic metals and bromine in the recovered polymer and HIPS waste was evaluated by X-ray fluorescence. The results are shown in Table 3. [Table 3]

[0130] As shown in Table 3, most of the inorganic additives were removed as insoluble matter. The recovered polymers contained almost no detectable levels of inorganic flame retardants.

[0131] The residue from centrifugation contained Sb and Br, as well as some microgels containing polymers. The residue was washed with the styrene-based polymer solvent p-cymene to remove residual HIPS. The remaining insoluble portion contained flame retardants and some microgels.

[0132] The remaining insoluble portion was dispersed in hot toluene or a copolymer of a good PbU and / or PBu swelling agent and centrifuged. The microgel containing the remaining polymer remained as a suspension, while the flame retardant settled at the bottom as pellets. The polymer and flame retardant (e.g., Sb) were then separated. Thus, each component is reusable.

[0133] While this disclosure has been described with reference to examples, it should be understood that the claims should not be limited by the embodiments specified in the examples, but rather should be given the broadest interpretation consistent with the overall description.

[0134] All publications, patents, and patent applications are incorporated herein by reference to the same extent that each individual publication, patent, or patent application is specifically and individually indicated to be incorporated by reference as a whole. Where any term in this disclosure is found to be defined differently in a document incorporated herein by reference, the definition provided herein shall be the definition for that term.

Claims

1. A method for recovering a flame retardant from styrene polymer waste, wherein the styrene polymer comprises the flame retardant and the styrene polymer, and the method is The styrene-based polymer waste is combined with a first solvent to obtain a soluble portion and an insoluble portion, and To separate the soluble portion from the insoluble portion. Includes, The flame retardant is substantially located in the soluble portion, and the styrene polymer is substantially located in the insoluble portion; or A method wherein the flame retardant is substantially contained in the insoluble portion, and the styrene polymer is substantially contained in the soluble portion.

2. The method according to claim 1, wherein the flame retardant is substantially contained in the soluble portion, and the styrene polymer is substantially contained in the insoluble portion.

3. The method according to claim 2, wherein the flame retardant is recovered from the soluble portion by solvent evaporation.

4. The method according to claim 2, further comprising combining the soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and optionally recovering the precipitated flame retardant by filtration, decantation, and / or centrifugation.

5. The method according to claim 2, further comprising washing the insoluble portion with one or more additional portions of the first solvent after the separation to obtain a washed portion and a washed insoluble portion.

6. The method according to claim 5, further comprising combining the cleaning portion and the soluble portion to obtain the combined soluble portion.

7. The method according to claim 6, further comprising recovering the flame retardant from the combined soluble portion by solvent removal, wherein the solvent removal optionally includes precipitation, crystallization, solvent evaporation, and a combination thereof.

8. The method according to claim 6, further comprising combining the combined soluble portion with a flame retardant non-solvent to selectively precipitate or crystallize the flame retardant, and optionally recovering the precipitated or crystallized flame retardant by filtration, decantation, and / or centrifugation.

9. The method according to any one of claims 2 to 8, wherein the flame retardant is selected from HBCD, PBDE, TBBPA, TBPC, octabromodiphenyl oxide (Octabrom), decabromodiphenyl oxide (DBDPO), and mixtures thereof.

10. The first solvent is a non-solvent for the styrene-based polymer, and the first solvent is C ５－８ Alkane, C １－５ The method according to any one of claims 2 to 9, wherein the first solvent is selected from alkyl alcohols, alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), and mixtures thereof, or the first solvent is a mixture of a benzene-based solvent (e.g., selected from p-cymene, ethylbenzene, toluene, and mixtures thereof) and a polar aprotic solvent (e.g., selected from alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), ethers, N,N-dialkylamides (e.g., DMF), and mixtures thereof).

11. The method according to claim 10, wherein the first solvent comprises pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, methyl ethyl ketone, ethyl acetate, DMF, ethyl acetate, p-cymene, ethylbenzene, toluene, and mixtures thereof.

12. The method according to any one of claims 2 to 11, further comprising washing the insoluble portion with one or more portions of a styrene polymer nonsolvent to obtain a washed insoluble portion, wherein the washing is optionally carried out at a temperature exceeding the glass transition state temperature (Tg) of the washed insoluble portion.

13. The styrene-based polymer nonsolvent is C ５－８ Alkane, C １－５ The method according to claim 12, wherein the nonsolvent of the styrene polymer is selected from alkyl alcohols and mixtures thereof, and optionally the nonsolvent of the styrene polymer is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

14. The method according to claim 12 or 13, further comprising drying the washed insoluble portion and recovering the styrene-based polymer.

15. The insoluble portion is combined with a second solvent to obtain a styrene-based polymer mixture; The styrene polymer mixture is heated to a temperature sufficient to dissolve the styrene polymer to obtain a styrene polymer solution; The styrene polymer solution is combined with a styrene polymer non-solvent to selectively precipitate the styrene polymer; and The precipitated styrene-based polymer may be optionally recovered by filtration, decantation, and / or centrifugation; and Optionally, wash the recovered styrene polymer with one or more additional portions of the styrene polymer non-solvent and dry the recovered styrene polymer. The method according to any one of claims 2 to 11, further comprising:

16. The method according to claim 15, wherein the second solvent is selected from the first solvent according to claim 10 or 11, cyclohexane, a mixture of acetone and a benzene-based solvent (e.g., p-cymene, toluene, ethylbenzene), and mixtures thereof.

17. The method according to claim 15 or 16, wherein the combination of the insoluble portion and the second solvent is carried out such that the styrene polymer is present in the styrene polymer mixture at an amount of about 5 wt% to about 30 wt%.

18. The method according to any one of claims 15 to 17, wherein the temperature is approximately room temperature (25°C) to approximately 100°C.

19. The method according to claim 1, wherein the flame retardant is substantially contained in the insoluble portion, and the styrene polymer is substantially contained in the soluble portion.

20. The method according to claim 19, further comprising drying the insoluble portion and recovering the flame retardant.

21. The method according to claim 20, further comprising washing the insoluble portion with one or more further portions of the first solvent to obtain a washed portion and a washed insoluble portion.

22. The method according to claim 21, further comprising drying the washed insoluble portion and recovering the flame retardant.

23. The method according to any one of claims 19 to 22, further comprising recovering the styrene polymer by solvent removal, wherein the solvent removal optionally includes solvent evaporation, precipitation, and / or crystallization.

24. The first solvent is C ５－８ Alkane, C １－５ The method according to any one of claims 19 to 23, wherein the first solvent is selected from alkyl alcohols and mixtures thereof, and optionally the first solvent is selected from pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

25. The method according to any one of claims 19 to 24, wherein the flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

26. The flame retardant is substantially in the insoluble portion, and the styrenic polymer is substantially in the soluble portion. The flame retardant includes an inorganic flame retardant, and optionally the inorganic flame retardant is Sb ２ O ３ , ammonium halide, metal hydroxide (for example, MgOH, aluminum trihydrate), Ca ３ (BO ３ ) ２ , inorganic nitrate (for example, ammonium nitrate), inorganic phosphate (for example, ammonium phosphate), inorganic phosphonate, and a mixture thereof, the method according to claim 1.

27. The method further comprises combining the soluble portion and the insoluble portion with a third solvent before separating the soluble portion and the insoluble portion to obtain a microgel in which the soluble portion contains a portion of the styrene polymer; and The separation of the soluble portion and the insoluble portion is carried out by centrifugation, and so the microgel of the styrene polymer exists as a suspension of the soluble portion and as a pellet of the insoluble portion, and Optionally, the third solvent can swell the styrene polymer or form a gel with the styrene polymer. The method according to claim 26, wherein optionally the third solvent is selected from p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

28. The method according to claim 27, wherein the microgel contains about 15 wt% to about 25 wt% of the styrene-based polymer.

29. The method according to claim 27 or 28, further comprising recovering the pellets and the flame retardant, and optionally washing the pellets with one or more further portions of the first solvent.

30. The inorganic flame retardant is Sb ２ O ３ The method according to any one of claims 26 to 29, including the method described in any one of claims 26 to 29.

31. The styrene-based polymer waste further comprises an inorganic pigment, optionally the inorganic pigment being TiO ２ The inorganic pigment is recovered together with the inorganic flame retardant, and optionally, the method includes the Sb ２ O ３ and the TiO ２ This further includes separating the Sb, optionally the separation being the Sb ２ O ３ The method according to claim 30, which is carried out by selectively solubilizing in a basic medium, wherein the basic medium optionally includes an aqueous hydroxide solution (e.g., KOH, NaOH, LiOH).

32. The method according to any one of claims 26 to 31, further comprising an organic flame retardant.

33. The method according to claim 32, wherein the organic flame retardant is selected from PBDE, TBBPA, TBPC, and mixtures thereof.

34. The method according to claim 32, wherein the organic flame retardant is selected from DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

35. The method according to any one of claims 32 to 34, further comprising separating the inorganic flame retardant from the organic flame retardant.

36. The method according to any one of claims 1 to 35, further comprising purifying the recovered flame retardant.

37. The method according to any one of claims 1 to 36, wherein the styrene polymer is selected from ABS, HIPS, atactic polystyrene (PS), SAN, SBS, syndiotactic PS, isotactic PS, styrene-methyl methacrylate (SMMA), methyl methacrylate-acrylonitrile-butadiene-styrene (MABS), methyl methacrylate-butadiene-styrene (MBS), and mixtures thereof.

38. The method according to claim 27, wherein the styrene-based polymer is selected from HIPS, ABS, and mixtures thereof.

39. The method according to claim 38, wherein the microgel contains the polybutadiene component of the styrene-based polymer.

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