Method for recovering flame retardant from styrene polymer waste

Abstract

The present disclosure relates to methods of 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 fraction and an insoluble fraction, separating the soluble and insoluble fractions, and the flame retardant is substantially in the soluble fraction and the styrene polymer is substantially in the insoluble fraction or vice versa.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to US 63 / 467,528 filed May 18, 2023, the entire contents of which are hereby incorporated by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a method of separating a flame retardant from a styrene polymer in a styrene polymer waste. The present disclosure further relates to a method of recovering a flame retardant from a styrene polymer waste. BACKGROUND

[0004] Post-consumer styrene polymer waste is often recycled to obtain recyclate polymer material that can be reused. Many post-consumer styrene wastes contain different chemical nature flame retardants that are difficult to separate from the polymer material. However, some of these flame retardants are valuable substances that can be reused or reused, while others are harmful to consumer health and can have been banned by the relevant authorities.

[0005] From this, there is a need to develop a method of separating different flame retardants from a styrene polymer in a styrene polymer waste. SUMMARY

[0006] It has been shown herein that, with the difference in solubility of different flame retardants and styrene polymers in various solvents, flame retardants can be separated and recovered from a styrene polymer waste.

[0007] From this, in one aspect, the present disclosure includes a method of recovering a flame retardant from a styrene polymer waste, the styrene polymer comprising a flame retardant and a styrene polymer, the method comprising

[0008] combining the styrene polymer waste with a first solvent to obtain a soluble fraction and an insoluble fraction, and

[0009] separating the soluble fraction and the insoluble fraction;

[0010] wherein

[0011] the flame retardant is substantially in the soluble fraction and the styrene polymer is substantially in the insoluble fraction; or

[0012] the flame retardant is substantially in the insoluble fraction and the styrene polymer is substantially in the soluble fraction.

[0013] In some embodiments, the flame retardant is substantially in the soluble fraction and the styrene polymer is substantially in the insoluble fraction.

[0014] In some embodiments, the method further comprises recovering the flame retardant from the soluble portion by solvent removal. In some embodiments, solvent removal comprises precipitation, crystallization, solvent evaporation, and combinations thereof.

[0015] In some embodiments, the method further comprises 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 by filtration, decantation, and / or centrifugation.

[0016] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of the first solvent after the separation to obtain a wash portion and a washed insoluble portion.

[0017] In some embodiments, the method further comprises combining the wash portion and the soluble portion to obtain a combined soluble portion.

[0018] In some embodiments, the method further comprises 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 by filtration, decantation, and / or centrifugation.

[0019] In some embodiments, the flame retardant is selected from the group consisting of HBCD, PBDE, TBBPA, TBPC, Octabrom, DBDPO, and mixtures thereof.

[0020] In some embodiments, the first solvent is a non-solvent for the styrenic polymer, and wherein the first solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 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 solvent (e.g., selected from the group consisting of p-cymene, ethylbenzene, toluene, and mixtures thereof) and a polar aprotic solvent (e.g., selected from the group consisting of alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), ethers, N,N,-dialkyl amides (e.g., DMF), and mixtures thereof).

[0021] In some embodiments, the first solvent comprises pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, methyl ethyl ketone, ethyl acetate, DMF, p-cymene, ethylbenzene, toluene, and mixtures thereof.

[0022] In some embodiments, the method further comprises washing the insoluble fraction with one or more portions of a styrene polymer non-solvent to obtain a washed insoluble fraction. In some embodiments, the washing is performed at a temperature above the glass transition temperature (Tg) of the washed insoluble fraction.

[0023] In some embodiments, the styrene polymer non-solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 alkyl alcohols, and mixtures thereof. In some embodiments, the styrene polymer non-solvent is selected from the group consisting of pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0024] In some embodiments, the method further comprises drying the washed insoluble fraction to recover the styrene polymer.

[0025] In some embodiments, the method further comprises

[0026] combining the insoluble fraction with a second solvent to obtain a styrene polymer mixture;

[0027] heating the styrene polymer mixture to a temperature sufficient to dissolve the styrene polymer to obtain a styrene polymer solution;

[0028] combining the styrene polymer solution with a styrene polymer non-solvent to selectively precipitate the styrene polymer; and

[0029] optionally recovering the precipitated styrene polymer by filtration, decanting, and / or centrifugation; and

[0030] optionally washing the recovered styrene polymer with one or more additional portions of the styrene polymer non-solvent and drying the recovered styrene polymer.

[0031] In some embodiments, the second solvent is selected from the group consisting of the first solvent as defined herein, mixtures of cyclohexane, acetone, and benzene solvents (e.g., p-cymene, toluene, ethylbenzene), and mixtures thereof.

[0032] In some embodiments, the combining of the insoluble fraction and the second solvent is performed such that the styrene polymer is present in the styrene polymer mixture at about 5 wt% to about 30 wt%.

[0033] In some embodiments, the temperature is about room temperature (25 °C) to about 100 °C.

[0034] In some embodiments, the flame retardant is substantially in the insoluble fraction and the styrene polymer is substantially in the soluble fraction.

[0035] In some embodiments, the method further comprises drying the insoluble fraction to recover the flame retardant.

[0036] In some embodiments, the method further comprises washing the insoluble fraction with one or more additional portions of the first solvent to obtain a washed fraction and a washed insoluble fraction.

[0037] In some embodiments, the method further comprises drying the washed insoluble fraction to recover the flame retardant.

[0038] In some embodiments, the method further comprises recovering the styrenic polymer by solvent removal. In some embodiments, the solvent removal comprises solvent evaporation, precipitation, and / or crystallization.

[0039] In some embodiments, the first solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 alkyl alcohols, and mixtures thereof. In some embodiments, the first solvent is selected from the group consisting of pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof, and mixtures thereof.

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

[0041] In some embodiments, the flame retardant is substantially in the insoluble fraction and the styrenic polymer is substantially in the soluble fraction, and wherein the flame retardant comprises an inorganic flame retardant. In some embodiments, the inorganic flame retardant is selected from the group consisting of Sb203, ammonium halides, metal hydroxides (e.g., MgOH, aluminum trihydrate), Ca3(BO3)2, inorganic phosphates (e.g., ammonium phosphate), and mixtures thereof.

[0042] In some embodiments, the method further comprises, prior to the separating the soluble fraction and the insoluble fraction, combining the soluble fraction and the insoluble fraction with a third solvent to obtain a microgel comprising a portion of the styrenic polymer in the soluble fraction; and

[0043] wherein the separating the soluble fraction and the insoluble fraction is performed by centrifugation, such that the microgel of the styrenic polymer is present in the soluble fraction as a suspension and the insoluble fraction is present as a pellet.

[0044] In some embodiments, the third solvent is capable of swelling the styrenic polymer or forming a gel with the styrenic polymer.

[0045] In some embodiments, the third solvent is selected from the group consisting of p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

[0046] In some embodiments, the microgel comprises about 15 wt% to about 25 wt% of the styrenic polymer. In some embodiments, the styrenic polymer is selected from HIPS, ABS, and mixtures thereof. It can be appreciated that both HIPS and ABS contain a polybutadiene component (e.g., an elastomeric domain of polybutadiene). In some embodiments, the microgel comprises the polybutadiene component of the styrenic polymer.

[0047] In some embodiments, the method further comprises recovering the pellets to recover the flame retardant, and optionally washing the pellets with one or more additional portions of the first solvent.

[0048] In some embodiments, the inorganic flame retardant comprises Sb203.

[0049] In some embodiments, the styrenic polymer waste further comprises an inorganic pigment, optionally the inorganic pigment comprises Ti02, wherein the inorganic pigment is recovered together with the inorganic flame retardant, and optionally wherein the method further comprises separating the Sb203and the Ti02, optionally by selectively dissolving the Sb203in an alkaline medium, optionally the alkaline medium comprises an aqueous hydroxide (e.g., KOH, NaOH, LiOH).

[0050] In some embodiments, the flame retardant further comprises an organic flame retardant.

[0051] In some embodiments, the organic flame retardant is selected from PBDE, TBBPA, TBPC, Octabrom, DBDPO, and mixtures thereof.

[0052] In some embodiments, the organic flame retardant is selected from DBDPE, N,N- ethylenbis(tetrabromophthalimide), tris(tribromoneopentyl)phosphate, and mixtures thereof.

[0053] In some embodiments, the method further comprises separating the inorganic flame retardant from the organic flame retardant.

[0054] In some embodiments, the method further comprises purifying the recovered flame retardant.

[0055] In some embodiments, the styrenic 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.

[0056] According to another aspect, the present disclosure includes a method of recovering a flame retardant from a polymer waste, the polymer comprising the flame retardant and a polymer, the method comprising

[0057] combining the polymer waste with a first solvent to obtain a soluble fraction and an insoluble fraction, and

[0058] separating the soluble fraction and the insoluble fraction;

[0059] wherein

[0060] the flame retardant is substantially in the soluble fraction and the polymer is substantially in the insoluble fraction; or

[0061] the flame retardant is substantially in the insoluble fraction and the polymer is substantially in the soluble fraction. BRIEF DESCRIPTION OF DRAWINGS

[0062] Embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings, in which:

[0063] Figure 1 A flowchart illustrating an exemplary method 100 of the present disclosure is shown.

[0064] Figure 2 A flowchart illustrating an exemplary method 200 of the present disclosure is shown.

[0065] Figure 3 A flowchart illustrating an exemplary method 300 of the present disclosure is shown, wherein a flame retardant that is insoluble in a first solvent is recovered, and wherein an optional soluble flame retardant can also be present in the styrenic polymer waste.

[0066] Other features and advantages of the present disclosure will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the present disclosure, are given by way of illustration only, and that the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the entire description. DETAILED DESCRIPTION

[0067] I. Definitions

[0068] The definitions and embodiments described in this section and other sections are intended to apply to all embodiments and aspects of the disclosure described herein for which they are applicable, as would be understood by a person of skill in the art, unless otherwise indicated.

[0069] The term “and / or” as used herein means that the listed items are individually present or combined, or used. In effect, the term means “at least one of” or “one or more of” the listed items is used or present.

[0070] As used in the present disclosure, the singular forms “a” and “the” include plural referents unless the context clearly dictates otherwise. For example, an embodiment that includes “a compound” is understood to present certain aspects with one compound or two or more additional compounds.

[0071] In embodiments that include an “additional” or “second” component (such as an additional or second solvent), the second component as used herein is chemically different from the other component or first component. A “third” component is different from the other components, the first component, and the second component, and further recited or “additional” components are similarly different.

[0072] As used in the disclosure and claims, the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “include” and “includes”) or “containing” (and any form of containing, such as “contain” and “contains”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0073] The terms “consisting of’ and grammatical variations thereof, as used herein, are intended to be closed terms, which specify the presence of the stated features, elements, components, groups, integers, and / or steps, and do not allow for the presence of other, unrecited features, elements, components, groups, integers, and / or steps.

[0074] The term “consisting essentially of’ as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and / or steps as well as those that do not materially affect the basic and novel characteristics of these features, elements, components, groups, integers, and / or steps.

[0075] The present specification refers to a number of chemical terms and abbreviations used by those skilled in the art. However, for clarity and consistency, definitions of selected terms are provided.

[0076] The terms “about,” “substantially,” and “approximately” as used herein represent reasonable variations in the modified term that do not materially change the final result. These degree terms are to be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the term it modifies or unless the context clearly indicates otherwise to one of skill in the art.

[0077] The term "styrene polymer" as used herein means a polymer, e.g., a homopolymer or a copolymer, in which at least one monomer is a styrene-based monomer or a vinyl aromatic monomer. For example, styrene polymers include homopolymers of styrene (i.e., polystyrene) and copolymers of styrene with one or more polymerizable monomers. For example, styrene polymers also include graft polymers, e.g., homopolymers or copolymers comprising at least one styrene-based monomer or vinyl aromatic-based monomer grafted to a non-styrene polymer, or homopolymers or copolymers comprising at least one styrene-based monomer or vinyl aromatic-based monomer grafted to one or more other homopolymers or copolymers comprising at least one styrene-based monomer or vinyl aromatic-based monomer. The copolymers can be block copolymers.

[0078] The term "styrene polymer waste" as used herein means a waste comprising at least one styrene polymer as described herein and a flame retardant.

[0079] As used herein, the term "non-solvent" with respect to a particular substance means a compound or mixture of compounds in which the substance is not substantially soluble. For example, a styrene polymer non-solvent refers to a compound or mixture of compounds in which a styrene polymer is not substantially soluble. For example, a flame retardant non-solvent refers to a compound or mixture of compounds in which one or more types of flame retardant is not substantially insoluble therein.

[0080] II. Methods of the Disclosure

[0081] The present disclosure relates to methods for recovering flame retardants from styrene polymer waste.

[0082] Referring to Figure 1 An example method 100 of the present disclosure is shown therein. At step 102, a styrene polymer waste to be recycled is combined with a first solvent. The styrene polymer waste is partially dissolved. At step 104, the soluble portion and the insoluble portion are separated. The flame retardant is present in either the soluble portion or the insoluble portion and can be recovered therefrom.

[0083] Referring to Figure 2 An example method 200 of the present disclosure is shown therein. At step 202, a styrene polymer waste to be recycled is combined with a first solvent. The styrene polymer waste is partially dissolved. At step 204, the soluble portion and the insoluble portion are separated. It is then determined at step 206 whether the flame retardant is in the soluble portion or the insoluble portion. The styrene polymer is in the other portion.

[0084] If the flame retardant is in the soluble fraction and the styrene polymer is in the insoluble fraction, the method moves to step 208, where the flame retardant is recovered from the soluble fraction by solvent removal. For example, solvent removal can be achieved by means known in the art, including but not limited to evaporation, selective precipitation, and crystallization. Optionally, as shown in step 212, the insoluble fraction can be washed with an additional portion of the first solvent to further extract any residual flame retardant in the insoluble fraction. To facilitate extraction of the residual flame retardant, the insoluble fraction can be combined with an amount of styrene polymer solvent to swell the styrene polymer into a gel or paste. The washing of step 212 can then be done at a higher temperature above the glass transition temperature (Tg) of the polymer gel or paste to keep the gel / paste more ductile, facilitating extraction of the residual flame retardant.

[0085] The washing portion of step 212 can be combined with the soluble fraction at step 214. The flame retardant can be extracted from the combined soluble fraction by solvent removal as described herein.

[0086] If it is determined that the flame retardant is in the insoluble fraction and the styrene polymer is in the soluble fraction, the method moves to step 210 to dry the insoluble fraction to recover the flame retardant. Optionally, at step 222, the insoluble fraction can be further washed with an additional portion of the first solvent to remove any residual polymer. The soluble fraction containing the styrene polymer can be used in optional step 220 to recover the styrene polymer by solvent removal as described herein.

[0087] Once the flame retardant is removed in steps 208 and 210, the recovered flame retardant can be purified by means known in the art, such as by recrystallization and / or column chromatography, as shown in step 218.

[0088] Referring to Figure 3 , an example method 300 of the present disclosure is shown, in which the flame retardant is present in the soluble fraction and the styrene polymer is present in the insoluble fraction. At step 302, the styrene polymer waste to be recycled is combined with a first solvent. The styrene polymer waste is partially dissolved. Optionally, at step 308, a styrene polymer non-solvent is combined with the mixture of soluble and insoluble fractions to obtain a microgel comprising a portion of the styrene polymer, with the remaining portion of the styrene polymer in the soluble fraction, prior to separating the soluble and insoluble fractions (304). The mixture resulting from step 308 can optionally be centrifuged at step 310, with the microgel remaining in suspension in the soluble fraction containing the styrene polymer. The insoluble flame retardant is deposited at the bottom as a centrifuged pellet. The mixture is then separated as shown in step 304.

[0089] As shown in step 312, the insoluble portion containing the flame retardant can optionally be washed with an additional portion of the first solvent to extract any polymer.

[0090] The soluble mixture resulting from step 304 can be assayed to see if it contains additional soluble flame retardant. If so, the soluble flame retardant or polymer can be selectively extracted by, for example, selective precipitation of the flame retardant or polymer (step 318). If not, the styrenic polymer can optionally be recovered by solvent removal at step 316.

[0091] In one aspect, the present disclosure includes a method of recovering a flame retardant from a styrenic polymer waste, the styrenic polymer comprising a flame retardant and a styrenic polymer, the method comprising

[0092] combining the styrenic polymer waste with a first solvent to obtain a soluble portion and an insoluble portion, and

[0093] separating the soluble portion and the insoluble portion;

[0094] wherein

[0095] the flame retardant is substantially in the soluble portion and the styrenic polymer is substantially in the insoluble portion; or

[0096] the flame retardant is substantially in the insoluble portion and the styrenic polymer is substantially in the soluble portion.

[0097] In some embodiments, the flame retardant is substantially in the soluble portion and the styrenic polymer is substantially in the insoluble portion.

[0098] In some embodiments, the method further comprises recovering the flame retardant from the soluble portion by solvent removal. In some embodiments, solvent removal comprises precipitation, crystallization, solvent evaporation, and combinations thereof.

[0099] In some embodiments, the method further comprises 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 by filtration, decanting, and / or centrifugation.

[0100] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of the first solvent after the separating to obtain a washed portion and a washed insoluble portion.

[0101] In some embodiments, the method further comprises combining the washed portion and the soluble portion to obtain a combined soluble portion.

[0102] In some embodiments, the method further comprises combining the soluble portion of the combination 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 performed by filtration, decantation, and / or centrifugation.

[0103] In some embodiments, the flame retardant is selected from the group consisting of HBCD, PBDE, TBBPA, TBPC, Octabrom, DBDPO, and mixtures thereof.

[0104] In some embodiments, the first solvent is a non-solvent for the styrene polymer, and wherein the first solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 alkyl alcohols, alkyl esters, alkyl ketones, and mixtures thereof, or the first solvent is a mixture of a benzene solvent (e.g., selected from the group consisting of p-cymene, ethylbenzene, toluene, and mixtures thereof) and a polar aprotic solvent (e.g., selected from the group consisting of alkyl esters (e.g., ethyl acetate), alkyl ketones (e.g., methyl ethyl ketone), ethers, N,N,-dialkyl amides (e.g., DMF), and mixtures thereof).

[0105] In some embodiments, 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.

[0106] In some embodiments, the method further comprises washing the insoluble portion with one or more portions of a styrene 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.

[0107] In some embodiments, the styrene polymer non-solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 alkyl alcohols, and mixtures thereof. In some embodiments, the styrene polymer non-solvent is selected from the group consisting of pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

[0108] In some embodiments, the method further comprises drying the washed insoluble portion to recover the styrene polymer.

[0109] In some embodiments, the method further comprises

[0110] combining the insoluble portion with a second solvent to obtain a styrene polymer mixture;

[0111] heating the styrene polymer mixture to a temperature sufficient to dissolve the styrene polymer to obtain a styrene polymer solution;

[0112] combining the styrene polymer solution with a styrene polymer non-solvent to selectively precipitate the styrene polymer; and

[0113] optionally recovering the precipitated styrene polymer by filtration, decanting, and / or centrifugation; and

[0114] optionally washing the recovered styrene polymer with one or more additional portions of the styrene polymer non-solvent and drying the recovered styrene polymer.

[0115] In some embodiments, the second solvent is selected from the first solvent as defined herein, a mixture of cyclohexane, acetone, and benzene solvents (e.g., p-cymene, toluene, ethylbenzene), and mixtures thereof.

[0116] In some embodiments, the combining of the insoluble portion and the second solvent is performed such that the styrene polymer is present in the styrene polymer mixture at about 5 wt% to about 30 wt%.

[0117] In some embodiments, the temperature is about room temperature (25 °C) to about 100 °C.

[0118] In some embodiments, the flame retardant is substantially in the insoluble portion and the styrene polymer is substantially in the soluble portion.

[0119] In some embodiments, the method further comprises drying the insoluble portion to recover the flame retardant.

[0120] In some embodiments, the method further comprises washing the insoluble portion with one or more additional portions of the first solvent to obtain a wash portion and a washed insoluble portion.

[0121] In some embodiments, the method further comprises drying the washed insoluble portion to recover the flame retardant.

[0122] In some embodiments, the method further comprises recovering the styrene polymer by solvent removal. In some embodiments, the solvent removal comprises solvent evaporation, precipitation, and / or crystallization.

[0123] In some embodiments, the first solvent is selected from C 5-8 alkanes, C 1-5 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, and mixtures thereof.

[0124] In some embodiments, the flame retardant is selected from DBDPE, N,N- ethylenedi(s-tetrabromophthalimide), tris(tribromoneopentyl)phosphate, and mixtures thereof.

[0125] In some embodiments, the flame retardant is substantially in the insoluble fraction and the styrene polymer is substantially in the soluble fraction, and wherein the flame retardant comprises an inorganic flame retardant. In some embodiments, the inorganic flame retardant is selected from the group consisting of Sb203, ammonium halides, metal hydroxides (e.g., MgOH, aluminum trihydrate), Ca3(BO3)2, inorganic nitrate salts (e.g., ammonium nitrate), inorganic phosphate salts (e.g., ammonium phosphate), inorganic phosphonate salts, and mixtures thereof.

[0126] As will be appreciated by one skilled in the art, inorganic flame retardants, and in particular Sb203, act as synergists for organic flame retardants. When used in combination, the amount of organic flame retardant can be reduced due to the presence of the synergist. Thus, the method of the present disclosure allows for the separation and recovery of synergists from styrene polymer waste.

[0127] In some embodiments, the method further comprises, prior to the separating the soluble fraction and the insoluble fraction, combining the soluble fraction and the insoluble fraction with a third solvent to obtain a microgel comprising a portion of the styrene polymer in the soluble fraction; and

[0128] wherein the separating the soluble fraction and the insoluble fraction is performed by centrifugation, such that the microgel of the styrene polymer is present in the soluble fraction as a suspension and the insoluble fraction is present as pellets.

[0129] In some embodiments, the third solvent is capable of swelling the styrene polymer or forming a gel with the styrene polymer. As will be appreciated, such a solvent will cause a portion of the styrene polymer or some component of the styrene polymer to swell into a microgel having a density similar to that of the soluble fraction. Thus, centrifugation of the mixture will allow the microgel to remain suspended and the insoluble fraction to settle.

[0130] In some embodiments, the third solvent is selected from the group consisting of p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

[0131] In some embodiments, the microgel comprises about 15 wt% to about 25 wt% of the styrene polymer. In some embodiments, the styrene polymer is selected from the group consisting of HIPS, ABS, and mixtures thereof. As will be appreciated, both HIPS and ABS contain a polybutadiene component (e.g., an elastomeric domain of polybutadiene). In some embodiments, the microgel comprises the polybutadiene component of the styrene polymer.

[0132] In some embodiments, the method further comprises recovering the pellets to recover the flame retardant, and optionally washing the pellets with one or more additional portions of the first solvent.

[0133] In some embodiments, the inorganic flame retardant comprises Sb203.

[0134] In some embodiments, the styrenic polymer waste further comprises an inorganic pigment, optionally the inorganic pigment comprises Ti02, wherein the inorganic pigment is recovered with the inorganic flame retardant, and optionally wherein the method further comprises separating the Sb203and the Ti02, optionally by selectively dissolving the Sb203in an alkaline medium, optionally the alkaline medium comprises an aqueous hydroxide (e.g., KOH, NaOH, LiOH).

[0135] In some embodiments, the flame retardant further comprises an organic flame retardant.

[0136] In some embodiments, the organic flame retardant is selected from the group consisting of PBDE, TBBPA, TBPC, and mixtures thereof.

[0137] In some embodiments, the organic flame retardant is selected from the group consisting of DBDPE, N,N-ethylenebis(tetrabromophthalimide), tris(tribromoneopentyl) phosphate, and mixtures thereof.

[0138] In some embodiments, the method further comprises separating the inorganic flame retardant from the organic flame retardant.

[0139] In some embodiments, the method further comprises purifying the recovered flame retardant.

[0140] In some embodiments, the styrenic polymer is selected from the group consisting of 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.

[0141] In some embodiments, the styrenic polymer is derived from a styrene-based monomer or a vinyl aromatic monomer copolymerized with one or more polymerizable monomers. For example, the one or more polymerized monomers can be an unsaturated nitrile. The unsaturated nitrile can include, but is not limited to, acrylonitrile, methacrylonitrile, ethyl acrylonitrile, fumaronitrile, and mixtures thereof.

[0142] In some embodiments, the styrenic polymer can be crosslinked and / or grafted with one or more other polymers. The one or more other polymers can include a polymerized conjugated olefin. For example, the conjugated olefin can include a diene, 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 olefin is 1,3-butadiene, isoprene, or mixtures thereof.

[0143] In some embodiments, the styrenic polymer is selected from the group consisting of acrylonitrile-butadiene styrene (ABS), high impact polystyrene (HIPS), styrene acrylonitrile copolymer (SAN), styrene butadiene styrene copolymer (SBS), and mixtures thereof.

[0144] In some cases, the skilled person can appreciate that it can be useful to select a styrenic polymer non-solvent having a boiling point near or slightly above the glass transition temperature (Tg) of the styrenic polymer to soften a gel formed by the styrenic polymer swelled with the solvent. For example, it can be desirable to heat a gel or microgel comprising a styrenic polymer and a styrenic polymer non-solvent to near the Tg of the styrenic polymer gel or microgel to facilitate removal of soluble flame retardants by washing the gel or microgel with additional portions of the styrenic polymer non-solvent at or near the boiling point of the non-solvent.

[0145] In some embodiments, the styrenic polymer non-solvent is selected from the group consisting of C 5-8 alkanes, C 1-6 alkyl alcohols, and mixtures thereof. It can be appreciated that a suitable non-solvent can be selected for a particular styrenic polymer of interest by means known in the art.

[0146] In some embodiments, the flame retardant non-solvent is selected from the group consisting of C 5-8 alkanes, C 1-6 alkyl alcohols, and mixtures thereof. It can be appreciated that a suitable non-solvent can be selected for a particular flame retardant of interest by means known in the art. For example, if the nature of the flame retardant present in the styrenic polymer waste is known or determined, a particular non-solvent can be selected accordingly.

[0147] In some embodiments, the recovered flame retardant is reused in the manufacture of a polymeric material. For example, the polymeric material can comprise a styrenic polymer or a non-styrenic polymer. For example, the polymeric material can comprise a thermoplastic and / or a thermoset plastic. For example, the polymeric material can comprise a polyolefin (e.g., polyethylene, polypropylene), a polycarbonate, an epoxy resin, a polyester, a polyamide, or mixtures or copolymers thereof.

[0148] In some embodiments, the styrene polymer waste further comprises inorganic pigments, such as Ti02. Inorganic pigments have similar insoluble characteristics as the inorganic flame retardants described herein. Thus, inorganic pigments can be recovered from the styrene polymer waste along with any inorganic flame retardants. Once the inorganic pigments and inorganic flame retardants have been recovered, they can be separated using methods known in the art. For example, some inorganic compounds can be selectively dissolved or precipitated in acidic or basic media. Thus, an acid or base can be added to the recovered inorganic compounds to selectively dissolve certain compounds. For example, it is known that Sb203is soluble in basic media, while Ti02is not. A mixture of Sb203and Ti02recovered from styrene polymer waste can be separated from one another by selectively dissolving the Sb203in a basic media (e.g., by adding an aqueous hydroxide solution) and filtering the solid Ti02. Both the inorganic pigments and the inorganic flame retardants can be reused, for example, in the manufacture of other polymeric materials.

[0149] In some embodiments, the purification of the recovered flame retardants comprises selective precipitation, recrystallization, column chromatography (e.g., silica column), or a combination thereof.

[0150] Examples

[0151] The following non-limiting examples illustrate the present disclosure.

[0152] General Methods

[0153] All solvents were chromatographic grade with high purity purchased from Sigma Aldrich. Flame retardants were also purchased from Sigma Aldrich or specialized suppliers of flame retardants. The X-ray fluorescence spectrophotometer used was a Bruker Titan SI.

[0154] Example 1 Solubility testing of flame retardants in different solvents

[0155] A number of common flame retardants have been tested for solubility 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.

[0156] Table 1 - Solubility of Flame Retardants

[0157]

[0158]

[0159] It is expected that flame retardants that are not completely soluble (e.g., partially soluble or mostly soluble) in a given solvent can be substantially dissolved by increasing the temperature of the solution.

[0160] Example 2 Recovery of brominated flame retardants and inorganic flame retardants from ABS

[0161] Model styrene polymer waste was prepared with ABS pellets and different brominated flame retardants. Mixture A was prepared with 10 g ABS pellets and 1 g 3,3',5,5'-tetrabromobisphenol A (TBBPA) in 90 g ethyl acetate. Mixture B was prepared with 10 g ABS pellets, 1 g N,N-ethylene-bis(tetrabromophthalimide) in 90 g ethyl acetate.

[0162] Both mixtures were stirred vigorously at room temperature for five hours. The resulting mixtures were centrifuged at 8500 rpm for 20 minutes. The supernatant was evaluated for bromine content using X-ray fluorescence. The results are shown in Table 2.

[0163] Table 2 - Br content of supernatant

[0164]

[0165] As shown in Table 2, N,N-ethylene-bis(tetrabromophthalimide) is not soluble in ethyl acetate and is removed by centrifuging the mixture.

[0166] The centrifuged residue from mixture B was analyzed to show that it contained N,N-ethylene-bis(tetrabromophthalimide) as well as some microgels containing polybutadiene (PBu). The residue was washed twice with 50 g ethyl acetate to further remove the soluble ABS fraction. The washed residue was dried at 100°C for two hours. The dried residue contained N,N-ethylene-bis(tetrabromophthalimide) which can be reused.

[0167] Alternatively, the residue from mixture B containing N,N-ethylene-bis(tetrabromophthalimide) and PBu and / or PBu copolymer microgels was dispersed in 100 g toluene or a good PBu and / or PBu copolymer swelling agent. The resulting mixture was heated to 60°C with stirring for five hours. The resulting mixture was centrifuged at 3000 rpm for five minutes. The microgels containing the PBu fraction remained suspended in the supernatant while the N,N-ethylene-bis(tetrabromophthalimide) settled at the bottom as pellets. The polymers PBu and N,N-ethylene-bis(tetrabromophthalimide) were separated and each can be reused.

[0168] As shown in Table 2, TBBPA is soluble in ethyl acetate and remains in the supernatant fraction of the centrifuged mixture A where ABS is also soluble.

[0169] The supernatant of mixture A is combined with 60 g of a styrene polymer non-solvent (e.g., heptane or methanol) to produce a paste. The combination is carried out at room temperature or a suitable temperature to maintain the polymer paste 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 non-solvent (e.g., heptane or methanol) at a temperature and solvent ratio to maintain the polymer as a paste above its Tg. Each wash portion is retained separately as fraction 2 and fraction 3. Fractions 1-3 are combined, and the solvent is evaporated to recover the TBBPA. The dried TBBPA is further purified by dissolving the remaining trace amounts of polymer in a solvent for styrene polymers such as p-cymene or a mixture of a styrene polymer solvent and a styrene polymer non-solvent (e.g., a mixture of p-cymene and heptane) in which the TBBPA is insoluble. Any remaining polymer in the recovered TBBPA is dissolved in the solvent. The solution is filtered to remove the soluble portion containing polymer (e.g., ABS, SAN, and small chain 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 by, for example, recrystallization.

[0170] Example 3 Recovery of inorganic flame retardants from post-consumer HIPS

[0171] A 30 g post-consumer HIPS waste is dissolved in p-cymene to make a solution containing 15 wt% HIPS waste. About 10 wt% of methanol is added to the solution. The resulting mixture is centrifuged at 8500 rpm for 20 min. The supernatant is recovered. 340 g of heptane is added to the supernatant to precipitate the polymer content. The precipitate is removed as a paste and washed at a temperature above its Tg. The content of various inorganic metals and bromine in the recovered polymer and HIPS waste is evaluated by X-ray fluorescence. The results are shown in Table 3.

[0172] Table 3 - Inorganic metal and Br content

[0173]

[0174] As shown in Table 3, most of the inorganic additives are removed as insolubles. The recovered polymer has almost no detectable level of inorganic flame retardants.

[0175] The residue from the centrifugation contains Sb and Br as well as some polymer-containing microgels. The residue is washed with the styrene polymer solvent p-cymene to remove the remaining HIPS. The remaining insoluble portion contains flame retardants and some microgels.

[0176] The remaining insoluble fraction is dispersed in hot toluene or a good PbU and / or PBu copolymer swelling agent and centrifuged. The microgels containing any remaining polymer remain in suspension while the flame retardant settles as pellets at the bottom. The polymer and flame retardant (e.g. Sb) are then separated. Each component can be reused accordingly.

[0177] While the disclosure has been described with reference to examples, it is to be understood that the scope of the claims is not to be limited by the foregoing examples but is to be given the full scope of the disclosure.

[0178] All publications, patents, and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present disclosure is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for that term.

Claims

1. A method of recovering a flame retardant from a styrenic polymer waste, the styrenic polymer comprising a flame retardant and a styrenic polymer, the method comprising combining the styrenic polymer waste with a first solvent to obtain a soluble fraction and an insoluble fraction, and separating the soluble fraction and the insoluble fraction; wherein the flame retardant is substantially in the soluble fraction and the styrenic polymer is substantially in the insoluble fraction; or the flame retardant is substantially in the insoluble fraction and the styrenic polymer is substantially in the soluble fraction.

2. The method of claim 1, wherein the flame retardant is substantially in the soluble fraction and the styrenic polymer is substantially in the insoluble fraction.

3. The method of claim 2, wherein the flame retardant is recovered from the soluble fraction by solvent evaporation.

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

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

6. The method of claim 5, further comprising combining the wash fraction and the soluble fraction to obtain a combined soluble fraction.

7. The method of claim 6, further comprising recovering the flame retardant from the combined soluble fraction by solvent removal, optionally solvent removal comprising precipitation, crystallization, solvent evaporation, and combinations thereof.

8. The method of claim 6, further comprising combining the combined soluble fraction 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, decanting, and / or centrifugation.

9. The method of any one of claims 2 to 8, the flame retardant is selected from the group consisting of HBCD, PBDE, TBBPA, TBPC, Octabrom, DBDPO, and mixtures thereof.

10. The process according to any one of claims 2 to 9, wherein the first solvent is a non-solvent for the styrene polymer, and wherein the first solvent is selected from C 5-8 alkanes, C 1-5 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 solvent (e.g. selected from p-cymene, ethyl benzene, 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,-dialkyl amides (e.g. DMF) and mixtures thereof).

11. The method of 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, ethyl benzene, toluene, and mixtures thereof.

12. The method of any one of claims 2 to 11, further comprising washing the insoluble fraction with one or more portions of a styrenic polymer non-solvent to obtain a washed insoluble fraction, optionally the washing is performed at a temperature higher than the glass transition temperature (Tg) of the washed insoluble fraction.

13. The method of claim 12, wherein the styrene polymer non-solvent is selected from the group consisting of C 5-8 alkanes, C 1-5 alkyl alcohols, and mixtures thereof, optionally the styrene polymer non-solvent is selected from the group consisting of pentane, hexane, heptane, octane, methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof.

14. The method of claim 12 or 13, further comprising drying the washed insoluble fraction to recover the styrenic polymer.

15. The method of any one of claims 2 to 11, further comprising: combining the insoluble portion with a second solvent to obtain a styrene polymer mixture; heating the styrene polymer mixture to a temperature sufficient to dissolve the styrene polymer to obtain a styrene polymer solution; combining the styrene polymer solution with a styrene polymer non-solvent to selectively precipitate the styrene polymer; and optionally recovering the precipitated styrene polymer by filtration, decanting, and / or centrifugation; and optionally washing the recovered styrene polymer with one or more additional portions of the styrene polymer non-solvent and drying the recovered styrene polymer.

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

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

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

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

20. The method of claim 19, further comprising drying the insoluble portion to recover the flame retardant.

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

22. The method of claim 21, further comprising drying the washed insoluble portion to recover the flame retardant.

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

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

25. The method of 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 method of claim 1, wherein the flame retardant is substantially in the insoluble portion and the styrene polymer is substantially in the soluble portion, and wherein the flame retardant comprises an inorganic flame retardant, optionally the inorganic flame retardant is selected from Sb2O3, an ammonium halide, a metal hydroxide (e.g., MgOH, aluminum trihydrate), Ca3(BO3)2, an inorganic nitrate (e.g., ammonium nitrate), an inorganic phosphate (e.g., ammonium phosphate), an inorganic phosphonate, and mixtures thereof.

27. The method of claim 26, wherein the method further comprises, prior to the separating the soluble portion and the insoluble portion, combining the soluble portion and the insoluble portion with a third solvent to obtain a microgel comprising a portion of the styrene polymer in the soluble portion; and wherein said separating said soluble fraction and said insoluble fraction is carried out by centrifugation, such that said microgel of said styrenic polymer is present in said soluble fraction as a suspension, and said insoluble fraction is present as pellets, and optionally wherein said third solvent is capable of swelling said styrenic polymer or forming a gel with said styrenic polymer, optionally wherein said third solvent is selected from the group consisting of p-cymene, toluene, benzene, ethylbenzene, ethyl acetate, acetone, MEK, and mixtures thereof.

28. The method of claim 27, wherein said microgel comprises from about 15 wt% to about 25 wt% of said styrenic polymer.

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

30. The method of any one of claims 26 to 29, wherein said inorganic flame retardant comprises Sb2O3.

31. The method of claim 30, wherein said styrenic polymer waste further comprises an inorganic pigment, optionally said inorganic pigment comprises TiO2, wherein said inorganic pigment is recovered together with said inorganic flame retardant, and optionally wherein said method further comprises separating said Sb2O3 and said TiO2, optionally said separating is carried out by selectively dissolving said Sb2O3 in an alkaline medium, optionally said alkaline medium comprises an aqueous hydroxide (e.g. KOH, NaOH, LiOH).

32. The method of any one of claims 26 to 31, wherein said flame retardant further comprises an organic flame retardant.

33. The method of claim 32, wherein said organic flame retardant is selected from the group consisting of PBDE, TBBPA, TBPC, and mixtures thereof.

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

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

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

37. The method of any one of claims 1 to 36, wherein said styrenic polymer is selected from the group consisting of 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 of claim 27, wherein said styrenic polymer is selected from the group consisting of HIPS, ABS, and mixtures thereof.

39. The method of claim 38, wherein said microgel comprises a polybutadiene component of said styrenic polymer.

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