Recovery of metal compounds from polymers obtained by anionic polymerization

Abstract

The invention relates to a method for preparation of a polymer product comprising a polymer obtained by anionic polymerization, wherein the metal salts derived from the anionic polymerization initiator are recovered from the product. The invention also relates to a polymer product obtained by the method.

Description

[0001] Recovery of metal compounds from polymers obtained by anionic polymerization

[0002] Description

[0003] The invention relates to a method for the preparation of a polymer product comprising a polymer obtained by anionic polymerization, wherein the metal salts derived from the anionic polymerization initiator are recovered from the product, and a polymer product obtained by the method. It also covers the recovery of metal compounds from polymers obtained by anionic polymerization.

[0004] Block copolymers of vinyl aromatics (e.g. styrene) and conjugated dienes (e.g. butadiene), in particular styrene butadiene block copolymers (SBC), are known for many years and are useful for a variety of purposes. It is known to combine polystyrene with SBC copolymers in order to achieve an impact resistant modified polystyrene. Block copolymers of styrene and butadiene are described e.g. in WO 2000 / 58380, WO 1995 / 35335 and US 4,939,208. Such block copolymers and their mixtures with other polymers can be used, e.g. for the preparation of polymer films, medical devices, adhesives, packaging, home appliances, as described e.g. in WO 2023 / 036920, WO 2021 / 074075, EP-A 0636654 and WO 2022 / 263445.

[0005] Block copolymers of vinyl aromatics and conjugated dienes are copolymers comprising a plurality of polymer segments (polymer blocks) which are arranged in series or are otherwise linked and have a (more or less) uniform composition. Depending on the structure and content of diene monomers, the polymers may exhibit elastomeric properties or rigid, non-elastomeric properties. As a whole, they may exhibit elastomeric behavior similar to a polydiene (such as polybutadiene) and are for example used as rubbers (styrene butadiene SB rubbers), or may behave as transparent, impact-resistant styrene polymers. For such block copolymers, the polydiene-rich blocks determine the elastomeric behavior and are referred to as the soft phase, and the rigid blocks (in particular pure polystyrene-rich blocks) are referred to as the hard phase.

[0006] Such block copolymers are normally prepared via anionic polymerization which involves “living” polymer chains (anionic living polymerization). Typically, block copolymers are obtained by carrying out polymerization until all the added monomer is consumed and then adding more monomers of the same or different type or mixtures of monomers. This process can be repeated several times. Linear block copolymers or star-shaped block copolymers can be obtained by reaction of the living polymer with monofunctional or poly-functional reactants. Linear block copolymers are described for example in US 3,507,934 and US 4,122,134. Star block copolymers are disclosed for example in US 4,086,298; US 4,167,545 and US 3,639,517. Anionic living polymerization is also useful for preparing homo-polymers and copolymers other than block-copolymers, e.g. if a narrow molecular weight distribution is desired.

[0007] In anionic polymerization processes, highly nucleophilic organometallic initiators are typically used, which include complexes of nucleophilic organic anions and metal cations. In industrial processes, organo-lithium compounds such as butyl lithium, in particular n- butyl lithium and sec-butyl lithium are commonly used as anionic polymerization initiators.

[0008] After initiation of an anionic polymerization reaction, the growing polymer chains remain active even after the monomers are consumed, and addition of further monomeric species leads to further growth of the polymer chains, unless the reaction is terminated, e.g. by addition of a terminating agent, such as an acid, or coupling agents with multiple centers with which the nucleophilic species can react.

[0009] This leads to neutralization of the nucleophilic anionic chain end and the formation of a salt of the metal cation from the organometallic initiator, which is not sufficiently reactive to allow further polymerization of the monomeric species. After termination of the anionic polymerization reaction, the salt of the metal cation typically remains in the polymer product during the further processing, and is not removed, as some physical properties of the obtained polymer are not significantly affected by small amounts of salts.

[0010] Climate change, environmental pollution, population growth and resource dependency trigger the ecological and economic necessity of the transition from a linear to a circular economy. Since many years, intensive efforts were made to develop processes for the recovery of raw materials from plastics. These efforts have not yet resulted in large-scale applications; however, a greater ecological awareness and a need for sustainable solutions have led to a growing interest in chemical recycling.

[0011] While different recycling methods for polymer waste were described earlier, these methods are mostly not concerned with components of polymer products that do not substantially affect the properties of the polymers as such, but are necessarily present therein. In the case of polymers obtained by anionic polymerization, the components include salts of metal cations originating from organometallic initiators, e.g. those discussed above.

[0012] On the one hand, these salts, while not substantially relevant for the properties of the polymer products as such, may have known or unknown effects on living organisms and / or the environment in general, which have not yet been fully investigated. For example, lithium salts can be used as medication for treatment of e.g. mental disorders, but can also lead to defects in growth and development in animals or to grave psychopathological problems in humans, if ingested with food or drinking water (see, e.g. “On the physiological function of lithium from a psychiatric view point”, J. H. Demling et al., Med Hypotheses 2001 , 57(4), Abstract). Exposure of the environment and / or of organisms to certain metal salts, such as lithium salts, should therefore be avoided.

[0013] On the other hand, from an economic perspective, it would be desirable to recover the metal salts present in polymer products obtained by anionic polymerization, in order to enable recycling thereof for further applications and to reduce overall consumption of natural resources.

[0014] While it is has not yet been shown to what extent these salts leach out into the environment when articles comprising polymers obtained by anionic polymerization are exposed to the environment, the risk of leaching should be reduced nonetheless, to avoid both the contamination of the environment and the loss of those salts as potential resources for further applications.

[0015] However, avoidance of exposure of the environment to articles comprising polymers obtained by anionic polymerization would be economically not feasible and difficult to accomplish. For example polymers that are obtained by anionic polymerization, such as styrene-butadiene block-copolymers, have properties that can be beneficial in certain outdoor applications and food packaging (e.g. for on-the-go). In order to avoid exposure of the environment to such block copolymers, the use of the block-copolymers for outdoor applications would have to be limited, which is not desirable, and any littering of packaging should be avoided, which is hardly possible.

[0016] Therefore, there is a need for methods that enable recycling of metal components for further applications, and can lead to reduction of exposure of the environment and / or living organisms to said metal compounds, without having to refrain from using polymers obtained by anionic polymerization.

[0017] It was now surprisingly found that the amount of metal compounds in polymer products obtained by anionic polymerization can be substantially reduced if the polymer products are subjected to a series of specific processing steps disclosed herein.

[0018] By reducing the amount of metal compounds in the polymer products, the risk of leaching of metal salts into the environment is reduced, and the metal compounds become available as a source of metal cations for further applications. One aspect of the invention is a method for the preparation of a polymer product (P1) comprising at least one polymer (P), comprising the steps: a) preparing a heterogeneous mixture from a polymer product (P2) obtained by anionic polymerization, comprising at least one polymer (P) and at least one salt of at least one metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+); at least one organic solvent (S1); and at least one aqueous solvent (S2), preferably water, wherein the heterogeneous mixture can undergo phase separation at a temperature between 15 and 100 °C, forming an organic phase (OP) and an aqueous phase (AP); b) allowing at least partial phase separation of an organic phase (OP) from an aqueous phase (AP), wherein the organic phase (OP) comprises the organic solvent (S1) and the polymer (P), and the aqueous phase (AP) comprises the aqueous solvent (S2) and at least one salt of the metal cation (M+); and c) isolating a polymer product (P1) comprising the polymer (P) from the organic phase (OP); d) optionally isolating at least one metal compound (M1) comprising the metal cation (M+) from the aqueous phase (AP).

[0019] The polymer product (P2) used in the method can be any polymer product obtained by anionic polymerization, provided it comprises at least one polymer (P) and at least one salt of at least one metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+). For example, the polymer product (P2) may be a component of a manufactured article, e.g. in polymer waste, preferably post-consumer waste and / or post-industrial waste, which is subjected to the method of the invention in the course of polymer waste recycling.

[0020] The polymer product (P2) may also be a product obtained directly from an anionic polymerization process, which is subjected to the method of the invention before being further processed or utilized for the manufacturing of articles.

[0021] When the polymer product (P2) is a component of a manufactured article, such as in polymer waste, the preparation of the heterogeneous mixture preferably involves preparing a melt of the polymer product (P2), which is then mixed with the organic solvent

[0022] (51) and the aqueous solvent (S2), and / or dissolving the polymer product (P2) in at least one organic solvent (S1) and combining the obtained solution with the aqueous solvent

[0023] (52) or a heterogeneous mixture thereof with the organic solvent (S1). When the polymer product (P2) is a product obtained directly from an anionic polymerization process, the preparation of the heterogeneous mixture preferably involves combining the reaction mixture from the anionic polymerization process with the organic solvent (S1) and the aqueous solvent (S2). If the anionic polymerization process is carried out in the organic solvent (S1), the preparation of the heterogeneous mixture may also be carried out by combining the reaction mixture with the aqueous solvent (S2), without adding more organic solvent (S1), or by combining the reaction mixture with more organic solvent (S1) and the aqueous solvent (S2), simultaneously or consecutively, and in any order, e.g. by diluting the reaction mixture with more organic solvent (S1) and then combining the diluted reaction mixture with the aqueous solvent (S2).

[0024] Preferably, the heterogeneous mixture is prepared by combining a solution of the polymer product (P2) in at least one organic solvent (S1) with the aqueous solvent (S2) or a heterogeneous mixture thereof with the organic solvent (S1). Preferably, the weight ratio of the organic solvent (S1) to the aqueous solvent (S2) is in the range of from 1 :10 to 10:1 , preferably from 1 :2 to 8:1 , more preferably from 1 :1 to 6:1 , more preferably from 2:1 to 5:1.

[0025] The polymer (P) may in principle be any polymer obtained by anionic polymerization of vinylic monomers.

[0026] Preferably, the polymer (P) comprises repeating units of at least one aromatic vinyl monomer such as styrene, alpha-methyl styrene and / or para-methyl styrene, more preferably styrene, repeating units of at least one conjugated diene monomer such as butadiene and / or isoprene, more preferably butadiene, or a combination thereof with each other and / or with repeating units of other monomers anionically copolymerizable with aromatic vinyl monomers and / or conjugated diene monomers. More preferably, the polymer (P) comprises repeating units of the at least one aromatic vinyl monomer and repeating units of the at least one conjugated diene monomer. More preferably, the polymer (P) comprises repeating units of styrene and repeating units of butadiene.

[0027] Preferred polymers (P) comprise 20 to 100% by weight, preferably 30 to 90% by weight, more preferably 50 to 80% by weight, more preferably 60 to 70% by weight, based on the total weight of the repeating units in polymer (P), of repeating units of the at least one aromatic vinyl monomer, in particular styrene, 0 to 80% by weight, preferably 10 to 70% by weight, more preferably 20 to 50% by weight, more preferably 30 to 40% by weight, based on the total weight of the repeating units in polymer (P), of repeating units of the at least one conjugated diene monomer, in particular butadiene, and 0 to 40% by weight, preferably 0 to 30% by weight more preferably 0 to 20% by weight, more preferably 0 to 10% by weight, based on the total weight of the repeating units in polymer (P), of further repeating units of monomers copolymerizable with styrene and / or butadiene. Some preferred polymers (P) comprise 100% by weight of repeating units of the at least one aromatic vinyl monomer, in particular styrene, based on the total weight of the repeating units in polymer (P).

[0028] Preferably, the polymer (P) is a block copolymer, more preferably a block copolymer comprising at least one block comprising repeating units of the at least one aromatic vinyl monomer and at least one block comprising repeating units of the at least one conjugated diene monomer.

[0029] Exemplary block copolymers suited as polymer (P) may comprise one or more of the following: i) at least one block of repeating units of the at least one aromatic vinyl monomer and at least one block of repeating units of the at least one conjugated diene monomer; preferably, the block of repeating units of the at least one aromatic vinyl monomer constitutes from 10 to 90% by weight, more preferably from 20 to 80%, more preferably 30 to 70% by weight, more preferably 40 to 60% by weight, based on the total weight of polymer (P), and the block of repeating units of the at least one conjugated diene monomer constitutes from 10 to 90% by weight, more preferably from 20 to 80%, more preferably 30 to 70% by weight, more preferably 40 to 60% by weight, based on the total weight of polymer (P); ii) at least one block of repeating units of the at least one aromatic vinyl monomer and at least one block of repeating units of a mixture of the at least one conjugated diene monomer and the at least one aromatic vinyl monomer; preferably, the block of repeating units of the at least one aromatic vinyl monomer constitutes from 10 to 90% by weight, more preferably from 20 to 80%, more preferably 30 to 70% by weight, more preferably 40 to 60% by weight, based on the total weight of polymer (P), and the block of repeating units of the mixture of repeating units constitutes from 10 to 90% by weight, more preferably from 20 to 80%, more preferably 30 to 70% by weight, more preferably 40 to 60% by weight, based on the total weight of polymer (P), wherein preferably the weight ratio of the repeating units of at least one aromatic vinyl monomer to the repeating units of the at least one conjugated diene monomer in the mixture is from 1 :3 to 3:1 , preferably from 1 :2 to 2: 1 , more preferably from 1 : 1.5 to 1 .5: 1 ; iii) at least two blocks of repeating units of the at least one aromatic vinyl monomer and at least one block of repeating units of the at least one conjugated diene monomer; preferably, each block of repeating units of the at least one aromatic vinyl monomer independently (more preferably both simultaneously), constitutes from 5 to 40% by weight, more preferably from 8 to 30%, more preferably 10 to 20% by weight, more preferably 12 to 18% by weight, based on the total weight of polymer (P), and the block of repeating units of the at least one conjugated diene monomer constitutes from 20 to 90% by weight, more preferably from 40 to 84%, more preferably 60 to 20% by weight, more preferably 64 to 76% by weight, based on the total weight of polymer (P); iv) at least two block of repeating units of the at least one aromatic vinyl monomer and at least one block of repeating units of a mixture of the at least one conjugated diene monomer and the at least one aromatic vinyl monomer; preferably, each block of repeating units of the at least one aromatic vinyl monomer independently (more preferably both simultaneously), constitutes from 5 to 40% by weight, more preferably from 8 to 30%, more preferably 10 to 20% by weight, more preferably 12 to 18% by weight, based on the total weight of polymer (P), and the block of repeating units of the mixture of repeating units constitutes from 20 to 90% by weight, more preferably from 40 to 84%, more preferably 60 to 80% by weight, more preferably 64 to 76% by weight, based on the total weight of polymer (P), wherein preferably the weight ratio of the repeating units of at least one aromatic vinyl monomer to the repeating units of the at least one conjugated diene monomer in the mixture is from 1 :3 to 3:1 , preferably from 1 :2 to 2:1 , more preferably from 1 :1.5 to 1.5:1 ; v) Combinations of any of the above, wherein the block copolymers are coupled using at least one coupling agent, thus forming linear, branched, star-shaped, comb-shaped or other structures; vi) Mixtures of any of the above.

[0030] Exemplary combinations and / or mixtures of block copolymers also include mixtures of block copolymers having chains of two or more different block sequences, wherein at least one block copolymer has a first block sequence, and at least one block copolymer has a second block sequence, and wherein the second block sequence comprises the first block sequence and at least one further block. Such mixtures may be prepared by adding further initiator during anionic polymerization of at least one monomer, or between consumption of at least one monomer and addition of further monomer.

[0031] The blocks obtained after addition of further initiator then correspond to the first block sequence, and the blocks obtained before addition of further initiator then correspond to the at least one further block. Preferably, the molar ratio of further initiator to the initiator (I) used at the start of the living anionic polymerization process is in the range of from 0.1 :1 to 10:1 , more preferably of from 0.5:1 to 5:1 , more preferably from 1 :1 to 4:1 , independently for each addition of further initiator. Also preferred are combinations, wherein these mixtures of block copolymers having chains of two or more different block sequences are coupled using at least one coupling agent, thus forming linear, branched, star-shaped, comb-shaped or other structures.

[0032] For these combinations and / or mixtures of block copolymers having chains of two or more different block sequences, following exemplary combinations of block sequences can be used, wherein S1 to S5 correspond to polymerized aromatic vinyl monomers (which can be the same or different, preferably the same, more preferably styrene) in different blocks; B1 to B3 correspond to polymerized conjugated diene monomers (which can be the same or different, preferably the same, more preferably butadiene) in different blocks; (hyphen) indicates the transition between two blocks; “ / “ (slash) indicates random or tapered copolymerization of repeating units surrounded by “(“ and “)” (parentheses); and X represents a residue of a terminating agent (such as a proton in case of an alcohol), or a coupling group derived from a coupling agent, present between two or more polymer chains of any of the above block copolymers:

[0033] 1) A first block sequence S2-(B1 / S3)-X and a second block sequence S1-S2-(B1 / S3)- X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the second block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 1 :1 to 6: 1 , more preferably from 2:1 to 5: 1 , more preferably from 3:1 to 4:1.

[0034] Furthermore, the amount of S1 is preferably in the range from 30 to 50 wt.-%, more preferably 35 to 45 wt.-%, the amount of S2 is preferably in the range from 15 to 35 wt.- %, more preferably 20 to 30 wt.-%, the amount of S3 is preferably in the range from 5 to 20 wt.-%, more preferably 10 to 15 wt.-%, the amount of B1 is in the range from 15 to 40 wt.-%, more preferably 20 to 30 wt.-%, each based on the total weight of repeating units in the mixture. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil.

[0035] 2) A first block sequence S2-(S3 / B1)-(S4 / B2)-S5-X and a second block sequence S1- S2-(S3 / B1)-(S4 / B2)-S5-X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the second block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 1 : 1 to 4: 1 , more preferably from 2:1 to 3:1. Furthermore, the amount of S1 is preferably in the range from 20 to 50 wt.-%, more preferably 30 to 40 wt.-%, the amount of S2 is preferably in the range from 10 to 30 wt.- %, more preferably 15 to 25 wt.-%, the amount of S3 is preferably in the range from 1 to 15 wt.-%, more preferably 5 to 10 wt.-%, the amount of S4 is preferably in the range from 1 to 20 wt.-%, more preferably 5 to 15 wt.-%, the amount of S5 is preferably in the range from 1 to 10 wt.-%, more preferably 2 to 5 wt.-%, the amount of B1 is in the range from 1 to 15 wt.-%, more preferably 2 to 10 wt.-%, the amount of B2 is in the range from 10 to 25 wt.-%, more preferably 15 to 20 wt.-%. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil.

[0036] 3) A first block sequence S3-(S4 / B2)-S5-X and a second block sequence S1-(S2 / B1)- S3-(S4 / B2)-S5-X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the second block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S2 / B1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 1 :1 to 4:1 , more preferably from 2:1 to 3:1. Furthermore, the amount of S1 is preferably in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-%, the amount of S2 is preferably in the range from 30 to 45 wt.-%, more preferably 35 to 40 wt.-%, the amount of S3 is preferably in the range from 10 to 30 wt.-%, more preferably 15 to 25 wt.-%, the amount of S4 is preferably in the range from 1 to 15 wt.-%, more preferably 5 to 10 wt.-%, the amount of S5 is preferably in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-%, the amount of B1 is in the range from 1 to 15 wt.-%, more preferably 2 to 10 wt.-%, the amount of B2 is in the range from 15 to 35 wt.-%, more preferably 20 to 30 wt.-%. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil.

[0037] 4) A first block sequence S4-(S5 / B3)-X and a second block sequence S1-(S2 / B1)- (S3 / B2)-S4-(S5 / B3)-X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the second block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S3 / B2 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 0.3:1 to 1.5:1 , more preferably from 0.5:1 to 1 :1.

[0038] Furthermore, the amount of S1 is preferably in the range from 1 to 15 wt.-%, more preferably 5 to 10 wt.-%, the amount of S2 is preferably in the range from 35 to 55 wt.-%, more preferably 40 to 50 wt.-%, the amount of S3 is preferably in the range from 20 to 35 wt.-%, more preferably 25 to 30 wt.-%, the amount of S4 is preferably in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-%, the amount of B1 is in the range from 1 to 15 wt.-%, more preferably 5 to 10 wt.-%, the amount of B2 is in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-% .-%, the amount of B3 is in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-%. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil.

[0039] 5) A first block sequence S2-B1-X and a second block sequence S1-S2-B1-X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the second block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 0.5:1 to 2:1 , more preferably from 1 :1 to 1.5:1. Furthermore, the amount of S1 is preferably in the range from 45 to 60 wt.-%, more preferably 50 to 55 wt.-%, the amount of S2 is preferably in the range from 15 to 30 wt.-%, more preferably 20 to 25 wt.-%, the amount of B1 is in the range from 15 to 35 wt.-%, more preferably 20 to 30 wt.-%. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil.

[0040] 6) A first block sequence S3-B2-X, a second block sequence S2-B1-S3-B2-X and a third block sequence S1-S2-B1-S3-B2-X. Preferably, the molar ratio of block copolymer chains having the first block sequence to the block copolymer chains having the third block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for B1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 1 :1 to 5:1 , more preferably from 2:1 to 4:1 , and the molar ratio of block copolymer chains having the second block sequence to the block copolymer chains having the third block sequence for such mixture and / or combination (i.e. the molar ratio of the further initiator added after consumption of monomers required for S1 to the initiator used at the beginning of the living anionic polymerization) is in the range of from 0.5:1 to 2:1 , more preferably from 1 :1 to 1.5:1.

[0041] Furthermore, the amount of S1 is preferably in the range from 30 to 50 wt.-%, more preferably 35 to 45 wt.-%, the amount of S2 is preferably in the range from 10 to 30 wt.- %, more preferably 15 to 25 wt.-%, the amount of S3 is preferably in the range from 15 to 25 wt.-%, more preferably 10 to 20 wt.-%, the amount of B1 is in the range from 1 to 15 wt.-%, more preferably 5 to 10 wt.-%, the amount of B2 is in the range from 0.5 to 10 wt.-%, more preferably 1 to 5 wt.-% .-%, the amount of B3 is in the range from 10 to 25 wt.-%, more preferably 15 to 20 wt.-%. Furthermore, X is preferably a residue of a coupling agent, more preferably an epoxidized oil. Where two consecutive blocks of the same monomer composition (such as S1-S2) are shown in the second block sequence, a single block is present that is longer than the respective block (such as S2) in the first block sequence.

[0042] Preferably, at least one terminal block of the block copolymer comprises more than 50% by weight, more preferably at least 60% by weight, more preferably at least 70% by weight, based on the terminal block, of repeating units of the at least one aromatic vinyl monomer.

[0043] For example, at least one terminal block of the block copolymer may consist essentially, or consist of repeating units of the at least one aromatic vinyl monomer. More preferably, all terminal blocks of the block copolymer comprise more than 50% by weight, more preferably at least 60% by weight, more preferably at least 70% by weight, based on the respective terminal block, of repeating units of the at least one aromatic vinyl monomer. For example, all terminal blocks of the block copolymer may consist essentially, or consist of repeating units of the at least one aromatic vinyl monomer.

[0044] Furthermore, preferably at least one block of the block copolymer consists essentially of repeating units of the at least one conjugated diene monomer or a mixture thereof with the at least one aromatic vinyl monomer. More preferably, at least one non-terminal block of the block-copolymer consists essentially of repeating units of the at least one conjugated diene monomer or a mixture thereof with the at least one aromatic vinyl monomer.

[0045] For example, the block copolymer is selected from styrene-b-butadiene-X block copolymers, styrene-b-(styrene-co-butadiene)-X block copolymers, styrene-b-butadiene-b-sty- rene-X block copolymers, styrene-b-(styrene-co-butadiene)-b-styrene block copolymers, styrene-b-(styrene-co-butadiene)-b-styrene-b-(styrene-co-butadiene)-b-styrene-X copolymers, or combinations of any of the above, wherein the block copolymers may be coupled using at least one coupling agent, thus forming linear, branched, star-shaped, comb-shaped or other structures. indicates the transition between blocks and “-co- “ indicates random or tapered copolymerization “X” represents a residue of a terminating agent (such as a proton in case of an alcohol), or a coupling group derived from a coupling agent, present between two or more polymer chains of any of the above block copolymers.

[0046] The block copolymer may be any type of block copolymer obtainable by anionic polymerization, e.g. a linear block copolymer, a branched block copolymer, a star-shaped block copolymer, a comb-shaped block copolymer, with transitions between the blocks that may be sharp and / or tapered. Methods for preparing suitable block copolymers are known, and are described, e.g. in “Practical Guide to Structures, Properties and Applications of Styrenic Polymers” (N. Niessner, D. Wagner; 2013; Smithers Rapra; Shawbury, Shrewsbury, Shropshire; pp. 82-87) and WO 2023 / 036920 and documents cited therein.

[0047] The at least one organic solvent (S1) and the at least one aqueous solvent (S2) used for preparing the heterogeneous mixture may be any organic and aqueous solvent, respectively, which together enable phase separation at a temperature between 15 and 100 °C, preferably between 18 and 90 °C, more preferably between 20 and 70 °C, more preferably between 20 and 60 °C, when mixed with the polymer product (P2).

[0048] Preferably, the organic solvent (S1) and the aqueous solvent (S2) also undergo phase separation at a temperature between 15 and 100 °C, preferably between 18 and 90 °C, more preferably between 20 and 70 °C, more preferably between 20 and 60 °C, if mixed alone, i.e. in the absence of the polymer product (P2).

[0049] In the context of the present invention, the expression “phase separation at a temperature between X and Y” means that at least one temperature between the specified values X and Y exists, at which phase separation occurs, and does not exclude the possibility that phase separation may occur at temperatures outside of this range. Preferably, phase separation occurs over the entire range between the specified values.

[0050] For example, the aqueous solvent (S2) may be water or a mixture of water with other solvents that forms a single homogeneous phase at a temperature between 15 and 100 °C. These other solvents may include, e.g., alcohols, ketones, aldehydes, glycols. Preferably, the aqueous solvent (S2) is water or a mixture thereof with an alcohol having 1 to 3 carbon atoms, more preferably water.

[0051] For example, the at least one organic solvent (S1) may be selected from hydrocarbon solvents, such as alkanes and cycloalkanes having 5 to 15 carbon atoms and aromatic solvents, and etheric solvents, such as linear or cyclic ethers having 4 to 22 carbon atoms.

[0052] In cases where the polymer product (P2) is prepared by anionic polymerization in the same organic solvent (S1) as the one used for the preparation of the heterogeneous mixture, the solvent (S1) is selected from solvents that, under the conditions of the anionic polymerization, essentially do not deactivate or terminate the anionic polymerization initiator or the nucleophilic polymeric anion (also disclosed as a “living anionic polymer chain”) generated during the polymerization. Preferably, the organic solvent (S1) is selected from the group consisting of hydrocarbon solvents and etheric solvents. More preferably, the organic solvent (S1) is selected from the group consisting of alkanes and cycloalkanes having 5 to 15 carbon atoms, preferably 5 to 10 carbon atoms, more preferably 5 to 7 carbon atoms, benzene and substituted benzene derivatives, e.g. aromatic solvents with 6 to 14 carbon atoms, such as toluene, xylenes, mesitylene, anisole, N,N-dimethylaniline, heteroaromatic solvents, and linear and cyclic ethers having 4 to 22 carbon atoms, preferably 4 to 10 carbon atoms, more preferably 4 to 7 carbon atoms, and mixtures thereof.

[0053] Preferably, the organic solvent is selected from the group consisting of n-pentane, n- hexane, n-heptane, cyclopentane, cyclohexane, diethyl ether, di-n-propylether, di-n-bu- tyl ether, di-n-pentyl ether, tetra hydrofuran, tetrahydropyran, toluene, and mixtures thereof. More preferably, the organic solvent (S1) is selected from the group consisting of tetrahydrofuran (THF), toluene, cyclohexane, and mixtures thereof, more preferably cyclohexane.

[0054] The salt of the at least one metal cation (M+) may be any salt of any metal cation that is generated or used for any purpose during the preparation of a polymer product by anionic polymerization.

[0055] For example, the salt may originate from an anionic polymerization initiator, which itself may be considered a salt or complex of a nucleophilic organic anion (R-) and a metal cation (M+), or any metal cation-containing additive used in the anionic polymerization reaction, such as randomizing agents, for example alkali metal alcoholates.

[0056] Preferably, the salt originates at least from an anionic polymerization initiator. More preferably, the salt comprises an alkali metal salt, more preferably a lithium salt.

[0057] For example, salts of the at least one metal cation (M+) present in the polymer product (P2) may comprise one or more of the following: unconsumed anionic polymerization initiator, which may be considered a salt of a nucleophilic organic anion (R-) and the metal cation (M+); complexes of nucleophilic polymeric anions (P-) and the metal cation (M+), which may be considered a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+); by-products that are generated due to the reaction of the anionic polymerization initiator or of the living polymer chain with components present in the polymerization process, such as a solvent and / or contaminants (e.g. by deprotonation of solvent, hydrolysis and / or oxidation); and products generated during termination of the anionic polymerization by addition of at least one terminating and / or coupling agent. While the polymer product generated during anionic polymerization, i.e. comprising living polymer chains, may be directly used as polymer product (P2) for the preparation of the heterogeneous mixture the anionic polymerization is preferably terminated before preparing the heterogeneous mixture, e.g. by addition of at least one terminating and / or coupling agent, which reacts with the nucleophilic polymeric anions and any traces of unconsumed anionic polymerization initiator, to form a salt of the at least one metal cation (M+) and at least one less reactive anion.

[0058] Therefore, the preparation of the heterogeneous mixture in step a) preferably comprises the steps: a1) performing anionic polymerization of at least one monomer (A1) in at least one organic solvent (S1), using at least one anionic polymerization initiator (I), which is a complex of at least one nucleophilic organic anion (R-) and at least one metal cation (M+), to obtain a composition (C1) comprising the organic solvent (S1) and a complex of at least one nucleophilic polymeric anion (P-) and the metal cation (M+); a2) terminating the anionic polymerization by combining the composition (C1) with at least one terminating and / or coupling agent (T1), to obtain a composition (C2) comprising the organic solvent (S1) and a polymer product (P2) comprising the polymer (P) and at least one salt of the metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+); a3) preparing a heterogeneous mixture from the composition (C2) and the aqueous solvent (S2).

[0059] The at least one salt of the metal cation (M+) obtained in steb a2) will typically comprise at least one salt of the metal cation (M+) and an anion generated from the terminating and / or coupling agent.

[0060] The anionic polymerization initiator (I) is a complex (or salt) of at least one nucleophilic organic anion (R-) and at least one metal cation (M+). In the context of the present invention, the terms “complex” and “salt” are used interchangeably for the combination of at least one metal cation with at least one anion, and includes cases where the cations and anions are coordinated to each other (e.g. by forming adducts, covalent bonds, dipolar interactions, ionic interactions or intermediate types of interactions), separated by solvent (or other) molecules or dissociated in solution.

[0061] Apart from the nucleophilic organic anions (R-) and the metal cations (M+), the initiator (I) may also comprise further components, such as solvent molecules that may be coordinated to the metal cation (M+) or nucleophilic organic anion (R-), or non-nucleophilic anions (e.g. inorganic anions such as halide) that may be coordinated to the metal cation (M+). The nucleophilic organic anion (R-) may be any organic anion having sufficient nucleophilicity to initiate the anionic polymerization. Preferably, the nucleophilic organic anion (R-) is a hydrocarbon anion, for example an alkyl anion and / or aryl anion, which may be optionally substituted. For example, the nucleophilic organic anion (R-) may be an alkyl anion, a phenyl anion, or a benzyl anion. Preferably the nucleophilic organic anion (R-) is an alkyl anion, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl. More preferably, the organic anion (R-) is selected from n-butyl, sec-butyl and tert-butyl, more preferably n-butyl or sec-butyl.

[0062] The metal cation (M+) may be any metal cation which does not impair the ability of the nucleophilic organic anion (R-) and of the generated living polymer chains (P-) to react with monomers (e.g. weakly electophilic cations). Often, cations of metals with an electronegativity of < 1.5, preferably < 1.3, more preferably of < 1.25, more preferably of < 1.1 are used as metal cations (M+). Preferably, the metal cation (M+) is selected from alkali metal cations and alkali earth metal cations, preferably Li+, Na+, K+, Mg2+, Ca2+and Ba2+cations, more preferably Li+, K+or Ca2+cations, more preferably Li+or K+cations, more preferably Li+cations.

[0063] Accordingly, the initiator (I) can be, e.g. an organolithium compound, an organosodium compound, an organopotassium compound, an organomagnesium compound (e.g. a Grignard reagent), an organocalcium compound (e.g. a calcium Grignard reagent), and / or an organobarium compound (e.g. a barium Grignard reagent). Preferably, the initiator (I) is an organolithium compound such as alkyl lithium, More preferably, the initiator (I) is n-butyl lithium, sec-butyl lithium or tert-butyl lithium, more preferably n-butyl lithium or sec-butyl lithium.

[0064] Preferably, the weight ratio of the polymerization initiator (I) to the at least one monomer (A1) used for the anionic polymerization is in the range of from 1 :100 to 1 :100000, more preferably from 1 :200 to 1 :50000, more preferably from 1 :300 to 1 :20000, more preferably from 1 :400 to 1 : 10000.

[0065] In step a1), the anionic polymerization initiator (I) may be combined with the at least one monomer (A1) in the solvent (S1) directly, or the nucleophilic organic anion (R-) may be optionally converted to a less reactive anion, which is then used to initiate the polymerization of the at least one monomer. For example, the nucleophilic organic anion (R-) may be subjected to a reaction with a 1 ,1 -diaryl ethylene, such as 1 ,1 -diphenylethylene, which serves as an indicator of the absence of moisture, but which is sufficiently nucleophilic to initiate anionic polymerization of certain monomers. Moreover, additives may be added to the reaction, which e.g. allow control of the order, in which monomers are introduced into the nucleophilic polymeric anions (P-). For example, randomizing agents may be added to the reaction, which enable random copolymerization of different monomers in individual portions of a polymer, or which change the way in which individual monomers are introduced into the nucleophilic polymeric anions (P-).

[0066] For example, alkali metal alcoholates, such as hindered potassium alcoholates, preferably potassium tert-butylate or potassium tert-amylate may be used, or polar coordinating additives may be added, if random co-polymerization of vinyl aromatic monomers and conjugated diene monomers is intended, or if transitions between blocks are not intended to be sharp. Suitable additives that affect the course of the anionic polymerization reaction are known in the art, and are disclosed, e.g. in “Practical Guide to Structures, Properties and Applications of Styrenic Polymers” of N. Niessner, D. Wagner; 2013; Smithers Rapra; Shawbury, Shrewsbury, Shropshire; pp. 82-87.

[0067] During the anionic polymerization reaction, the nucleophilic organic anion (R-) (or a less reactive anion produced therefrom) reacts with the monomer (A1) thereby forming at least one nucleophilic polymeric anion (P-). This nucleophilic polymeric anion (P-), also described as a “living” polymer chain, reacts with monomer (A1) until all monomer (A1) is consumed, and remains active, even after consumption of monomer (A1), thereby forming a composition (01) comprising the organic solvent (S1) and a complex of at least one nucleophilic polymeric anion (P-) and the metal cation (M+).

[0068] If needed, the anionic polymerization reaction may be resumed by addition of further monomers, which may be the same as, or different from monomer (A1), to increase the length of the living polymer chain (P-) in the composition (01 ), which allows the preparation of block copolymers, wherein each block may have the same or a different composition of repeating units.

[0069] In the process, additional initiator (I) can optionally be added during the anionic polymerization reaction, or after consumption of at least one monomer and before addition of further monomers, which allows further variation of the structure of the final polymer product.

[0070] The monomer (A1) may be any monomer that can undergo anionic polymerization, to form at least one nucleophilic polymeric anion (P-). Suitable monomers are vinylic unsaturated monomers such as aromatic vinyl monomer such as styrene, alpha-methyl styrene and / or para-methyl styrene, more preferably styrene, conjugated diene monomers such as butadiene and / or isoprene, more preferably butadiene, or a combination thereof with each other and / or with other monomers copolymerizable with aromatic vinyl monomers and / or conjugated diene monomers. More preferably, the monomers used in the anionic polymerization comprise at least one aromatic vinyl monomer and at least one conjugated diene monomer. More preferably, the monomers used in the anionic polymerization are styrene and butadiene. Preferably, these monomers are used in the anionic polymerization reaction in an order that leads to the polymers (P) described above, in particular the block-copolymers described above.

[0071] In step a2), the anionic polymerization reaction is terminated by combining the composition (C 1 ) with at least one terminating and / or coupling agent (T1), to obtain a composition (C2), which comprises the solvent (S1) used in the anionic polymerization, and a polymer product (P2) comprising the polymer (P) and at least one salt of the metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+).

[0072] The terminating and / or coupling agent (T1) may be any terminating and / or coupling agent that can react with the nucleophilic polymeric anion (P-), thereby reducing the reactivity of the polymer chains to such extent that no reaction with further monomers can take place.

[0073] For example, terminating agents may be selected from compounds that transfer a proton or other cationic group (such as a Lewis-acid) to the nucleophilic polymeric anion (P-), thereby forming a polymer (P), or compounds that transfer a non-cationic group to the nucleophilic polymeric anion (P-), thereby forming a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+).

[0074] Suitable terminating agents that transfer a proton to nucleophilic polymeric anion (P-), thereby forming a polymer (P), include water, alcohols, amines, thiols and other Bronsted acids that have a lower acid constant (PKA) than the protonated form of the polymeric anion (P-).

[0075] Suitable terminating agents that transfer other cationic groups to the nucleophilic polymeric anion (P-), thereby forming a polymer (P) include, e.g., triorganyl oxonium, trior- ganyl sulfonium or carbenium salts, which transfer an organyl cation to the nucleophilic polymeric anion (P-), or halogenated organic compounds, which may undergo nucleophilic substitution and / or transfer a halonium cation to the nucleophilic polymeric anion (P-). Further terminating agents that transfer cationic groups to the nucleophilic polymeric anion (P-), thereby forming a polymer (P), include neutral carbonyl compounds that release anionic leaving groups when reacting with nucleophiles, e.g. acyl halides, which formally transfer an acyl cation to the nucleophilic polymeric anion (P-), and release a halide anion. Suitable terminating agents that transfer a non-cationic group to the nucleophilic polymeric anion (P-), thereby forming a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+), include ethers, (which react with carbanions at elevated temperatures), preferably cyclic ethers, more preferably epoxides, carbonyl compounds, such as ketones, aldehydes, carboxylic acid esters, carboxylic anhydrides, amides and imides, lactones and lactams. While some of these compounds may further polymerize under suitable conditions, e.g. formaldehyde, which may form polyoxymethylene, or cyclic ethers, lactones and lactams, which may undergo ring-opening polymerization, these compounds are still considered terminating agents for anionic polymerizations of vinylic unsaturated monomers in the context of the present invention, since polymerization of further vinylically unsaturated monomers (which typically require that the nucleophilic polymeric anion (P-) is a carbanion) is disabled after addition of these compounds.

[0076] Preferably, the terminating agents result in the formation of hydroxide and / or alcoholate anionic moieties.

[0077] In cases, where a terminating agent can react with two or more molecules of the nucleophilic polymeric anion (P-), thereby connecting the two or more molecules to each other, the terminating agent functions as a coupling agent. Suitable coupling agents may be, e.g. organic compounds comprising two or more functional groups that can react with a nucleophilic polymeric anion (P-), or compounds comprising functional groups that can react with two or more molecules of nucleophilic polymeric anions (P-), by forming a covalent bond therewith. For example, coupling agents may comprise an organic linking moiety and two or more groups selected from cyclic ether groups, preferably epoxide groups, carbonyl compounds, or groups that undergo nucleophilic substitution when exposed to carbanions such as nucleophilic polymeric anions (P-).

[0078] Compounds such as acyl halides, carboxylic acid esters, carboxylic anhydrides, amides, imides, lactones and lactams, which may release anionic leaving groups when reacting with nucleophiles, may also be used as coupling agents, since the carbonyl group of these compounds may react two or more times with nucleophilic polymeric anions (P-). Preferable coupling agents are epoxidized oils, more preferably epoxidized soybean oil. Coupling agents may be useful, e.g. in the preparation of star-shaped, branched and / or comb shaped block copolymers.

[0079] Other suitable terminating and / or coupling agents (T1) are known to those skilled in the art and may be selected depending on the intended product. Preferably, the terminating and / or coupling agent (T1) comprises, more preferably consists of, epoxides, alcohols and water, preferably epoxidized oils, such as epoxidized vegetable oils, preferably epoxidized soybean oil, 2-propanol and / or water.

[0080] Termination of the anionic polymerization reaction with the terminating and / or coupling agent (T1) leads to the formation of a composition (C2) comprising the organic solvent (S1) and a polymer product (P2) comprising the polymer (P) and at least one salt of the metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+).

[0081] The terminal end of the polymer (P) or the anionic precursor thereof, and the salt of the metal cation (M+) depends on the particular terminating and / or coupling agent (T1) used for termination of the anionic polymerization reaction. For example, where water is used as terminating agent, the obtained polymer (P) is the protonated form of the nucleophilic polymeric anion (P-) and the salt is the hydroxide of the metal cation (M+). Where an alcohol, such as 2-propanol, is used as terminating agent, the obtained polymer (P) is also the protonated form of the nucleophilic polymeric anion (P-), but the salt is the respective alcoholate, such as 2-propanolate of the metal cation (M+). Where an epoxide or carbonyl compound is used as terminating agent, a salt of at least one anionic precursor of a polymer (P) and at least one metal cation (M+) is formed, wherein the anionic precursor of polymer (P) has an anionic alcoholate terminal end.

[0082] Where an epoxidized oil is used as coupling agent, a salt of at least one anionic precursor of a polymer (P) and at least one metal cation (M+) is formed, wherein the anionic precursor of polymer (P) comprises two or more polymer chains that are linked to each other by a linker derived from the oil, comprising alcoholate functions attached thereto. Since epoxidized oils typically include both epoxide functions and ester functions (fatty acid esters of glycerol), termination of the anionic polymerization may occur via reaction of the nucleophilic polymeric anion (P-) both with epoxide functions and with the ester functions, which have glycerol-derived leaving groups.

[0083] Therefore, if epoxidized oils are used as coupling agents, the polymer product (P2) may contain a mixture of multiple salts of the at least one metal cation (M+), including salts with the at least one anionic precursor of a polymer (P), salts of deprotonated glycerol (glycerol alcoholates) and salts of deprotonated monoglycerides and diglycerides, as well as salts of further reaction products thereof.

[0084] If a the terminating and / or coupling agent (T1) is used as a coupling agent, the amount thereof is substoichiometric, compared to the amount of nucleophilic polymeric anions (P-) (which essentially corresponds to the amount of initiator (I) used in step a1)). Preferably, the amount of the terminating and / or coupling agent (T1) is then selected, thus that the molar ratio of functional groups of the coupling agent to initiator used in step a1), is in the range of from 0.1 :1 to 5:1 , preferably from 0.5:1 to 2:1 , more preferably from 0.7:1 to 1.2:1.

[0085] If the terminating and / or coupling agent (T1) is used only as a terminating agent, a molar excess of the terminating agent may be used. Preferably, the amount of terminating and / or coupling agent (T1) is then selected, thus that the molar ratio of the terminating agent to the initiator (I) used in step a1) is at least 1 :1 , preferably at least 1.5:1 , more preferably at least 2:1 , more preferably at least 5:1.

[0086] The termination of the anionic polymerization may be carried out, e.g. by adding the terminating and / or coupling agent (T1) to the composition (01), or by adding the composition (C1) to the terminating and / or coupling agent (T1). In cases where the terminating and / or coupling agent (T1) can function as a coupling agent, but the use is intended only for termination (without coupling), the composition (C1) is preferably added to the terminating and / or coupling agent (T1). In cases where the terminating and / or coupling agent (T1) is the aqueous solvent (S2), the step a2) of terminating the anionic polymerization can be combined with the step a3) of preparing a heterogeneous mixture, as described below, i.e. the composition (C1) can be combined directly with the aqueous solvent (S2), thereby in situ forming the composition (C2).

[0087] In step a3), a heterogeneous mixture is prepared from the composition (C2) and the aqueous solvent (S2). The heterogeneous mixture may be prepared by any suitable means known in the art, e.g. by combining the composition (C2) and the aqueous solvent (S2) or a mixture thereof with additional organic solvent (S1), and agitating the combination by suitable means such as stirring, shaking, ultrasonic treatment, or by combining the composition (C2) and the aqueous solvent (S2) in such a way that the liquid with the lower density is distributed below the liquid with the higher density, and allowing the liquid with the lower density to rise, thereby causing agitation.

[0088] This may, e.g. be carried out by allowing the liquid with lower density to rise through the liquid with higher density from a structure with a multitude of openings, such as a plate or conduit with holes, or a frit, in order to increase the contact surface between the composition (C2) and the aqueous solvent (S2). Preferably, the heterogeneous mixture is prepared by feeding or injecting a stream of the composition (C2) into the aqueous solvent (S2) at a position below the surface of the aqueous solvent (S2), or into the aqueous phase of a two-phase mixture comprising an organic solvent (S1) and the aqueous solvent (S2). Such preparation of a heterogeneous mixture may be carried out in a suitable vessel, such as a decanter, as depicted in FIG. 1. When the composition (C2) is brought into contact with the aqueous solvent (S2), preferably water, at least a portion of the anions of the polymer product (P2) present in the composition (C2) that are not hydroxide anions react with water present in the aqueous solvent (S2), resulting in protonation of said anions and the formation of hydroxide anions.

[0089] Where the anions present in the composition (C2) after protonation have a significantly higher acid constant PKA than water (preferably a PKA of 15 or higher, more preferably of 16 or higher, more preferably 17 or higher), such as in the case of alcoholates (e.g. 2- propanolate, glycerol alcoholate and / or polymer alcoholate anions), complexes of the nucleophilic polymeric anion (P-) and the metal cation (M+) and other salts of anionic precursors of a polymer (P) and the metal cation (M+), the protonation of the respective anions and the formation of hydroxide anions typically proceeds almost quantitatively.

[0090] During preparation of the heterogeneous mixture, at least 95 mol-%, often at least 99 mol-%, in particular at least 99.9 mol-% of these anions are protonated. Accordingly, any complexes of nucleophilic polymeric anions (P-) and the metal cations (M+) and other salts of anionic precursors of a polymers (P) and the metal cations (M+) are converted to polymers (P) and hydroxide of the metal cations (M+).

[0091] In step b), the heterogeneous mixture prepared in step a) is allowed to phase separate into an organic phase (OP) and an aqueous phase (AP), wherein the organic phase (OP) comprises the organic solvent (S1) and the polymer (P), and the aqueous phase (AP) comprises the aqueous solvent (S2) and at least one salt of the metal cation (M+). Phase separation may be carried out under any suitable conditions, e.g. at a temperature between 15 and 100 °C, at which the organic solvent (S1) and the aqueous solvent (S2) are known to undergo phase separation.

[0092] Preferably, phase separation of the heterogeneous mixture is allowed to proceed without active cooling or heating of the heterogeneous mixture. For example, the phase separation may be allowed to proceed at room temperature (e.g. 23-25 °C), however, the temperature of the heterogeneous mixture may be higher than room temperature due to exothermic reactions in step b) or residual heat from the previous steps, or may be lower than room temperature due to dissolution effects.

[0093] During the preparation of the heterogeneous mixture in step a) and the phase separation in step b), a majority of salts of the at least one metal cation (M+) present in the polymer product (P2) is transferred to the aqueous phase (AP), and a majority of the at least one polymer (P) remains in the organic phase (OP), which allows separation of the metal cation (M+) from the polymer (P). Typically, at least 60 mol-%, for example 75 mol-% to 99.9 mol-%, 80 to 99 mol-% or 90 to 98 mol-% of the metal cations (M+) present in the polymer product (P2) are transferred to the aqueous phase (AP). Further optional extraction steps with at least one aqueous solvent (S2) can further increase the amount of metal cations (M+) removed from the organic phase (OP). It has been found that, by the process according to the invention, metal cations (M+), in particular lithium cations, are removed from the organic phase (OP) particularly well if present as hydroxide salts.

[0094] In step c), a polymer product (P1) comprising the polymer (P) is isolated from the organic phase (OP). Isolation may be carried out by any means known in the art, e.g. by withdrawing the organic phase (AP) from the phase-separated heterogeneous mixture, removing the volatile components of the organic phase (OP), such as the organic solvent (S1), precipitation, distillation, adsorption, extraction, filtration, drying, etc.. The obtained polymer product (P1) comprising the polymer (P) may be further processed and / or used in the same way and for the same purposes as similar polymer products obtained by anionic polymerizations known in the art. For example, the polymer product (P1) may be used for the preparation of articles, or may be blended with other polymeric and / or non- polymeric components, to obtain molding compositions.

[0095] However, compared with conventional polymer products obtained by anionic polymerization, the polymer product (P1) has a significantly lower amount of salts of metal cations (M+). Therefore, the risk of leaching of metal cations (M+) into the environment and potentially harming the environment or living organisms exposed to articles comprising the polymer product (P1) is substantially reduced compared to conventional polymer products obtained by anionic polymerization.

[0096] Preferably, the organic solvent (S1) from the organic phase (OP) is recycled, dried and used in a subsequent process, e.g. a process according to the present invention.

[0097] Optionally, the salts of the metal cation (M+) present in the aqueous phase (AP) may be subjected to a reaction with further components, resulting in derivatization of the salts of the metal cation (M+). For example, hydroxide anions present in the aqueous phase (AP) may be subjected to a reaction with carbon dioxide, thus that carbonate anions and / or bicarbonate anions are formed.

[0098] The obtained carbonate and / or bicarbonate, preferably carbonate of the metal cation (M+) may be isolated as a metal compound (M1) in a subsequent step. Alternatively, the salts of the metal cation (M+) present in the aqueous phase (AP), preferably the hydroxide of the metal cation (M+) may be isolated as a metal compound (M 1 ) without a reaction with further components. Preferably, at least one metal compound (M1) comprising the metal cation (M+) is isolated in a step d) from the aqueous phase (AP). Isolation may be carried out by any means known in the art, e.g. by withdrawing the aqueous phase (AP) from the phase- separated heterogeneous mixture, removing the volatile components of the aqueous phase (AP), such as the aqueous solvent (S2), precipitation, distillation, adsorption, extraction, (nano)filtration, drying, etc.. Preferably, the at least one metal compound (M1) is the carbonate, phosphate or the hydroxide of the metal cation (M+).

[0099] Typically, at least 50 mol-%, for example 70 mol-% to 99 mol-%, 75 to 90 mol-% or 80 to 85 mol-% of the metal cations (M+) present in the polymer product (P2) can be isolated as the metal compound (M1) from the aqueous phase (AP).

[0100] The obtained metal compound (M1) comprising the metal cation (M+) may be used directly as a source of metal cations (M+) or may be further valorised, by methods known in the art. For example, the metal compound (M1) may be used directly as a salt in a process requiring such salt, or may be subjected to electrochemical processes, such as fused-salt electrolysis, in order to obtain the corresponding metal, which then can be used to prepare an initiator for further anionic polymerization reactions.

[0101] This allows recycling and utilization of the metal cations (M+), which would otherwise remain in the polymer product of an anionic polymerization reaction, and thus would be unavailable as a resource.

[0102] Preferably, the aqueous solvent (S2) from the organic phase (AP) is recycled and used in a subsequent process, e.g. a process according to the present invention.

[0103] In a preferred embodiment of the process of the invention, the organic solvent (S1) has a lower density than the aqueous solvent (S2), and the heterogeneous mixture in step a) is prepared by introducing, preferably injecting, a continuous or batch-wise stream comprising the polymer product (P2), into the bottom layer of a two-phase mixture comprising the organic solvent (S1) and the aqueous solvent (S2), and wherein the polymer product (P1) is continuously or batch-wise isolated from the top layer of the two-phase mixture, and the metal compound (M 1) is continuously or batch-wise isolated from the bottom layer of the two-phase mixture.

[0104] In a further preferred embodiment of the process of the invention, the organic solvent (S1) has a lower density than the aqueous solvent (S2), and the heterogeneous mixture in step a) is prepared by introducing, preferably injecting, a continuous or batch-wise stream comprising the polymer product (P2) and the organic solvent (S1) into the aqueous solvent (S2), and wherein the polymer product (P1) is continuously or batch-wise isolated from the top layer of the generated two-phase mixture, and the metal compound (M1) is continuously or batch-wise isolated from the bottom layer of the two-phase mixture. Where the metal compound (M1) is continuously isolated from the bottom layer of the two-phase mixture, water is preferably continuously added to the two-phase mixture, to ensure a constant volume of the aqueous phase. An illustration of such processes is shown in FIG. 1.

[0105] Another aspect of the invention is a polymer product (P1) obtained by the method of the invention, preferably wherein the polymer product (P1) comprises the at least one polymer (P), and from 0.001 to 400 mg, preferably from 0.01 to 300 mg, more preferably from 0.1 to 250 mg, more preferably from 1 to 200 mg of metal cations (M+) per kg of the polymer (P).

[0106] The polymer product (P1) of the invention has a significantly reduced content of metal cations (M+), compared with the initial content of metal cations (M+), that were introduced into the anionic polymerization reaction in the form of the polymerization initiator (I), and optionally further components. Typically, the polymer product (P1) comprises the polymer (P) and not more than 40 mol-%, preferably 0.1 to 25 mol-%, more preferably 1 to 20 mol-%, more preferably 2 to 10 mol-%, of the initial amount of metal cations (M+).

[0107] Yet another aspect of the invention is a heterogeneous mixture as defined above, obtained from a polymer product (P2) obtained by anionic polymerization, comprising at least one polymer (P) and at least one salt of at least one metal cation (M+), and / or a salt of at least one anionic precursor of polymer (P) and at least one metal cation (M+); at least one organic solvent (S1); and at least one aqueous solvent (S2), preferably water, wherein the heterogeneous mixture can undergo phase separation at a temperature between 15 °C and 100 °C, forming an organic phase (OP) and an aqueous phase (AP).

[0108] Moreover, an aspect of the invention is the use of a heterogeneous mixture comprising at least one organic solvent (S1) as defined above and at least one aqueous solvent (S2) as defined above, for separating at least one metal compound from at least one polymer product obtained by anionic polymerization.

[0109] The invention is further illustrated by the Figures, examples and claims.

[0110] FIG. 1 discloses an apparatus that can be used for carrying out the method of the invention, and a schematic depiction of an embodiment of the method. The shown apparatus is a vessel, such as a decanter, in which phase separation of a heterogeneous mixture comprising an aqueous phase (AP) and an organic phase (OP) can be carried out.

[0111] A polymer product (P2) comprising at least one polymer and at least one salt of at least one metal cation, and / or a salt of at least one anionic precursor of the polymer and at least one metal cation is fed into the vessel at a position below the surface of the aqueous phase. The organic phase (OP) is withdrawn from the side of the vessel and further processed to obtain a polymer product (P1) comprising at least one polymer. The aqueous phase (AP) is withdrawn from the bottom of the vessel and further processed to obtain a metal compound (M1).

[0112] Example 1

[0113] An exemplary styrene-butadiene block copolymer (SBC) was synthesized using standard procedures with the following linear block structure recipe: styrene-b-(styrene-co-butadiene)-b-styrene block copolymer, where the styrene terminal blocks each constitute 16 wt% of the block copolymer and the middle block is a randomized styrene-co-butadiene block with 34 wt% of styrene and 34 wt% of butadiene (all percentages based on the total weight of the block copolymer).

[0114] The process was carried out more in detail as follows:

[0115] A pilot reactor having a volume of 50 L, equipped with a stirrer and a thermometer, was charged with 13.3 kg of cyclohexane and heated to 50 °C. 2 mL of diphenylethylene were added and stirring was initiated. 1 g of a 13.8 wt% solution of sec-butyllithium in cyclohexane was added to the stirred solution, until a color change was observed, indicating that no moisture is present in the reaction mixture, after which another 25 g of the 13.8 wt% solution were added. Then, 3.3 g of a 5 wt% potassium tert-amylate solution in cyclohexane were added to the solution as a randomizing agent.

[0116] 672 g of styrene were added and the reaction was allowed to proceed until all monomer was consumed. After this, a mixture of 1428 g of styrene and 1428 g of butadiene were added and the reaction was allowed to proceed until all monomer was consumed. After this, further 672 g of styrene were added and the reaction was allowed to proceed until all monomer was consumed.

[0117] The complete consumption of monomers in each step was indicated by a peak in the temperature profile of the reaction mixture. To terminate the reaction, 25 mL of isopropanol were added, followed by 5 kg of deionized water, and the reaction mixture was stirred for 30 min at 90 rpm. The stirring was stopped, and the reaction mixture was left standing for 1 h at 25 °C, to allow phase separation. The aqueous phase was withdrawn from the bottom of the reactor.

[0118] The organic solvent was removed from the organic phase by distillation, and the polymeric solid residue was processed into granules using standard methods.

[0119] By acid-base titration of the aqueous phase using aqueous HCI (0.1 mol / L), a concentration of 214 mg / L of LiOH was determined.

[0120] Compared to the theroretical maximum of 257 mg / L, this corresponds to a recovery of Li+cations of 83%.

[0121] The polymer granules were analyzed using inductively coupled plasma mass spectrometry (ICP-MS).

[0122] The results showed that the granules contained 4 mg of lithium cations per kg of polymer.

[0123] Compared to the theoretical maximum of 93 mg of lithium cations, this corresponds to a reduction of lithium cations in the polymer by 95%. The polymer granules could be further processed to polymer blends and articles by standard procedures. The physical properties of the resultant products are substantially the same as those of corresponding products, where the lithium salts were not removed.

[0124] Similar results are obtained if 8.75 g of epoxidized linolein as coupling agent is added instead of 25 mL of isopropanol, or if the reaction mixture is injected into water for termination.

[0125] The styrene-butadiene block copolymer (SBC) of Example 1 can be used in thermoplastic SBC compositions and for making e.g. moulded parts for various applications, see “Practical Guide to Structures, Properties and Applications of Styrenic Polymers” of Norbert Niessner.

Claims

Claims1. A method for the preparation of a polymer product (P1) comprising at least one polymer (P), comprising the steps: a) preparing a heterogeneous mixture from a polymer product (P2) obtained by anionic polymerization, comprising at least one polymer (P) and at least one salt of at least one metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+); at least one organic solvent (S1); and at least one aqueous solvent (S2), preferably water, wherein the heterogeneous mixture can undergo phase separation at a temperature between 15 and 100 °C, forming an organic phase (OP) and an aqueous phase (AP); b) allowing at least partial phase separation of an organic phase (OP) from an aqueous phase (AP), wherein the organic phase (OP) comprises the organic solvent (S1) and the polymer (P), and the aqueous phase (AP) comprises the aqueous solvent (S2) and at least one salt of the metal cation (M+); and c) isolating a polymer product (P1) comprising the polymer (P) from the organic phase (OP); d) optionally isolating at least one metal compound (M1) comprising the metal cation (M+) from the aqueous phase (AP).

2. The method according to claim 1 , wherein the preparation of a heterogeneous mixture in step a) comprises the steps: a1) performing anionic polymerization of at least one monomer (A1) in at least one organic solvent (S1), using at least one anionic polymerization initiator (I), which is a complex of at least one nucleophilic organic anion (R-) and at least one metal cation (M+), to obtain a composition (C1) comprising the organic solvent (S1) and a complex of at least one nucleophilic polymeric anion (P-) and the metal cation (M+); a2) terminating the anionic polymerization by combining the composition (C1) with at least one terminating and / or coupling agent (T1), to obtain a composition (C2) comprising the organic solvent (S1) and a polymer product (P2) comprising the polymer (P) and at least one salt of the metal cation (M+), and / or a salt of at least one anionic precursor of the polymer (P) and at least one metal cation (M+); a3) preparing a heterogeneous mixture from the composition (C2) and the aqueous solvent (S2).

3. The method according to claim 2, wherein the nucleophilic organic anion (R-) is a hydrocarbon anion, preferably an alkyl and / or aryl anion, which is optionally substituted, more preferably an alkyl anion, a phenyl anion or a benzyl anion, which is optionallysubstituted, more preferably an alkyl anion, and the metal cation (M+) is an alkaline metal cation or an alkaline earth metal cation, preferably an alkaline metal cation, more preferably a lithium cation.

4. The method according to claim 2 or 3, wherein the terminating and / or coupling agent (T1) comprises at least one compound selected from an epoxide, an alcohol and water, preferably an epoxidized oil, 2-propanol and water.

5. The method according to any one of claims 2 to 4, wherein the monomer (A1) comprises at least one monomer selected from the group consisting of aromatic vinyl monomers, preferably styrene, and conjugated diene monomers, preferably butadiene.

6. The method according to any one of claims 1 to 5, wherein the polymer (P) is styrene homopolymer or a block-copolymer comprising at least one block comprising styrene repeating units and at least one block comprising butadiene repeating units or both butadiene and styrene repeating units.

7. The method according to any one of claims 1 to 6, wherein the at least one organic solvent (S1) comprises, preferably consists of at least one aliphatic or aromatic hydrocarbon or an ether, preferably an aliphatic hydrocarbon, toluene, tetrahydrofuran or a mixture thereof, more preferably cyclohexane.

8. The method according to any one of claims 1 to 7, wherein the metal compound (M1) is the carbonate or the hydroxide of the metal cation (M+).

9. The method according to any one of claims 1 to 8, wherein the polymer product (P2) comprises alcoholate anions, preferably 2-propanolate, glycerol alcoholate and / or polymeric alcoholate anions and the metal cations (M+), which form a mixture comprising hydroxide anions and metal cations (M+) when the heterogeneous mixture is prepared, wherein the hydroxide of the metal cation (M+) is isolated as the metal compound (M1) in step d).

10. The method according to any one of claims 1 to 8, wherein the aqueous phase (AP) comprises hydroxide anions and the metal cations (M+), and the hydroxide anions are subjected to a reaction with carbon dioxide, thus that carbonate anions and / or bicarbonate anions are formed, wherein the carbonate and / or bicarbonate of the metal cation (M+) is isolated as the metal compound (M1) in step d).

11. The method according to any one of claims 1 to 10, wherein the isolation of the metal compound (M 1 ) in step d) and / orfurther processing thereof comprises one or moresteps selected from extraction, evaporation, distillation, adsorption, filtration, precipitation and electrochemical separation.

12. The method according to any one of claims 1 to 11 , wherein the organic solvent (S1) has a lower density than the aqueous solvent (S2), and the heterogeneous mixture in step a) is prepared by introducing, preferably injecting, a continuous or batch-wise stream comprising the polymer product (P2), into the bottom layer of a two-phase mixture comprising the organic solvent (S1) and the aqueous solvent (S2), or by introducing, preferably injecting, a continuous or batch-wise stream comprising the polymer product (P2) and the organic solvent (S1) into the aqueous solvent (S2), and wherein the polymer product (P1) is continuously or batch-wise isolated from the top layer of the obtained two-phase mixture, and the metal compound (M1) is continuously or batch-wise isolated from the bottom layer of the two-phase mixture.

13. A polymer product (P1) obtained by the method according to any one of claims 1 to 12, preferably wherein the polymer product (P1) comprises the at least one polymer (P), and from 0.001 to 400 mg, preferably from 0.01 to 300 mg, more preferably from 0.1 to 250 mg, more preferably from 1 to 200 mg of metal cations (M+) per kg of the polymer (P).

14. A heterogeneous mixture as defined in any one of claims 1 to 12, obtained from: a polymer product (P2) obtained by anionic polymerization, comprising at least one polymer (P) and at least one salt of at least one metal cation (M+), and / or a salt of at least one anionic precursor of polymer (P) and at least one metal cation (M+); at least one organic solvent (S1); and at least one aqueous solvent (S2), preferably water, wherein the heterogeneous mixture can undergo phase separation at a temperature between 15 °C and 100 °C, forming an organic phase (OP) and an aqueous phase (AP).

15. The use of a heterogeneous mixture comprising at least one organic solvent (S1) as defined in any one of claims 1 to 12 and at least one aqueous solvent (S2) as defined in any one of claims 1 to 12, for separating at least one metal compound from at least one polymer product obtained by anionic polymerization.

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