Tailored coupling of anionic block copolymers for an increased balance between hardness and thermal stability

Abstract

The invention relates to a method for the preparation of a polymer product (P1) by living anionic polymerization, wherein a coupling agent (C) and optionally a terminating agent (T) are used to form coupled polymer chains (P-P) and terminated polymer chains (P). The obtained polymer product (P1) typically has lower Shore hardness, higher Vicat softening temperature or a combination thereof compared with polymer products having a similar melt volume rate and molecular weight, but prepared by unidirectional anionic polymerization.

Description

[0001] Tailored coupling of anionic block copolymers for an increased balance between hardness and thermal stability

[0002] Description

[0003] The invention relates to a method for the preparation of a polymer product (P1) by living anionic polymerization, wherein a coupling agent (C) and optionally a terminating agent (T) are used to form coupled polymer chains (P-P) and terminated polymer chains (P). The invention also relates to a polymer product (P1) obtained by said method.

[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.

[0005] 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, WO 2022 / 263445.

[0006] 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, i.e. blocks consisting either of pure styrene or with a low butadiene content, are referred to as the hard phase.

[0007] 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 mono-functional 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.

[0008] Anionic living polymerization is also useful for preparing homopolymers and copolymers other than block-copolymers, e.g. if a narrow molecular weight distribution is desired.

[0009] 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.

[0010] 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.

[0011] Block copolymers made from vinyl aromatics and conjugated dienes are widely used in medical plastics (e.g. medical tubing, drip chambers etc.), soft grips and flooring due to their highly customizable property profiles. However, in a large number of applications, transport and storage of the finished products can be hampered by low dimensional stability at temperatures above room temperature (23 °C). This is particularly relevant when the materials (such as tubes or drip chambers) are shipped over long distances and in warm climates. As a result of the elevated temperatures, the products tend to deform plastically and are often no longer suitable for their final application.

[0012] It has now been surprisingly found that polymer products obtained by living anionic polymerization exhibit improved dimensional stability at temperatures above room temperature (defined by a higher VICAT softening point) while maintaining a similar hardness level and / or exhibit a lower hardness (defined by a lower Shore hardness), while maintaining a similar dimensional stability at temperatures above room temperature, compared with polymer products obtained by unidirectional anionic polymerization having a similar weight average molecular weight, processability (defined by the melt volume rate) and polymer block structure, if these polymer products contain a mixture of coupled polymer chains and terminated polymer chains.

[0013] One aspect of the present invention is, therefore, a method for the preparation of a polymer product (P1) by living anionic polymerization comprising the steps: i) performing anionic polymerization of at least one monomer (A) using at least one anionic polymerization initiator (I), which comprises an initiator complex of at least one nucleophilic carbanion (R-) and at least one metal cation (M+), to obtain a reaction mixture comprising at least one polymeric complex of at least one nucleophilic polymeric carbanion (P-) and at least one metal cation (M+), with repeating units of the at least one monomer (A) incorporated therein; and ii) terminating the anionic polymerization by combining the reaction mixture, comprising at least one complex of at least one nucleophilic polymeric carbanion (P-) and at least one metal cation (M+), with at least one coupling agent (C) and optionally at least one terminating agent (T), to obtain a polymer product (P1), wherein the at least one coupling agent (C) has a functionality fcof at least 2, preferably 2 to 4, more preferably 2 to 3, more preferably 2, where the functionality fcdefines the maximum number of nucleophilic polymeric carbanion (P-) molecules that can be coupled together by the coupling agent (C) to form coupled polymer chains (P-P), and wherein the following condition applies:

[0014] / c - n(C) + n(T) > n(P’), where n(P") is the molar amount of nucleophilic polymeric carbanions (P-) used in step ii), n(C) is the molar amount of the at least one coupling agent (C) used in step ii), and n(T) is the molar amount of the optional at least one terminating agent (T) used in step ii), wherein the at least one coupling agent (C) and the amount thereof and optionally the at least one terminating agent (T) and the amount thereof, which are combined with the at least one nucleophilic polymeric carbanion (P-) in step ii), are selected, thus that a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) to form coupled polymer chains (P-P) and a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) and / or the at least one terminating agent (T) to form terminated polymer chains (P), where the terminated polymer chains (P) comprise polymer chains (Pc) that were terminated by the at least one coupling agent (C) and / or polymer chains (PT) that were terminated by the at least one terminating agent (T), and where the polymer product (P1) obtained in step ii) comprises a mixture of terminated polymer chains (P) and coupled polymer chains (P-P). Anionic polymerization in step i) can be carried out by any means known in the art for anionically polymerizing at least one monomer (A) using at least one anionic polymerization initiator (I), which comprises an initiator complex of at least one nucleophilic carbanion (R-) and at least one metal cation (M+).

[0015] For example, anionic polymerization is carried out in an organic solvent that is substantially inert towards nucleophilic carbanions at the conditions at which the polymerization takes place. For example, anionic polymerization can be carried out in at least one organic solvent 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. Preferably, the organic solvent is selected from the group consisting of hydrocarbon solvents and etheric solvents.

[0016] More preferably, the organic solvent 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. More 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-butyl ether, di-n-pentyl ether, tetrahydrofuran, tetrahydropyran, toluene, and mixtures thereof. More preferably, the organic solvent is selected from the group consisting of tetrahydrofuran (THF), toluene, cyclohexane, and mixtures thereof, more preferably cyclohexane.

[0017] The anionic polymerization initiator (I) used in the anionic polymerization is an initiator complex (or salt) of at least one nucleophilic organic carbanion (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.

[0018] 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 carbanion (R-), or non-nucleo- philic anions (e.g. inorganic anions such as halide) that may be coordinated to the metal cation (M+). The nucleophilic organic carbanion (R-) may be any organic anion having sufficient nucleophilicity to initiate the anionic polymerization. Preferably, the nucleophilic organic carbanion (R-) is a hydrocarbon anion, for example an alkyl anion and / or aryl anion, which may be optionally substituted. For example, the nucleophilic organic carbanion (R- ) may be an alkyl anion, a phenyl anion, or a benzyl anion. Preferably, the nucleophilic organic carbanion (R-) is an alkyl anion, such as methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl, sec-butyl or tert-butyl. More preferably, the organic carbanion (R-) is selected from n-butyl, sec-butyl and tert-butyl, more preferably n-butyl or sec-butyl.

[0019] The metal cation (M+) may be any metal cation which does not impair the ability of the nucleophilic organic carbanion (R-) and of the generated living polymer chains (P-) to react with monomers (e.g. weakly electrophilic 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.

[0020] 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.

[0021] Preferably, the weight ratio of the polymerization initiator (I) to the at least one monomer (A) 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.

[0022] In step i), the anionic polymerization initiator (I) may be combined with the at least one monomer (A) directly, or the nucleophilic organic carbanion (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 carbanion (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-).

[0023] 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 (such as tapered transitions). 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” (N. Niessner, D. Wagner; 2013; Smithers Rapra; Shawbury, Shrewsbury, Shropshire; pp. 82-87).

[0024] During the anionic polymerization reaction, the nucleophilic organic carbanion (R-) (or a less reactive anion produced therefrom) reacts with the monomer (A) thereby forming at least one nucleophilic polymeric carbanion (P-). This nucleophilic polymeric carbanion (P-), also described as a “living” polymer chain, reacts with monomer (A) until all monomer (A) is consumed, and remains active, even after consumption of monomer (A), thereby forming a composition comprising a polymeric complex of at least one nucleophilic polymeric carbanion (P-) and the metal cation (M+).

[0025] If needed, the anionic polymerization reaction may be resumed by addition of further monomers, which may be the same as, or different from monomer (A), to increase the length of the living polymer chain (P-), which allows the preparation of block copolymers, wherein each block may have the same or a different composition of repeating units.

[0026] 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.

[0027] The monomer (A) may be any monomer that can undergo anionic polymerization, to form at least one nucleophilic polymeric carbanion (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 mixtures thereof with butadiene, more preferably, styrene and butadiene.

[0028] Preferably, the at least one monomer (A) is used in step i) in a sequence leading to a homopolymer of at least one aromatic vinyl (preferably styrene) repeating unit, or a block copolymer comprising at least one block of aromatic vinyl (preferably styrene) repeating unit and at least one block comprising at least one conjugated diene (preferably butadiene) repeating unit or a mixture thereof with at least one aromatic vinyl (preferably styrene) repeating unit. More preferably, the first (and thus terminal) block of the block copolymer obtained by the anionic polymerization is a block of aromatic vinyl (preferably styrene) repeating units.

[0029] In step ii), the anionic polymerization is terminated by combining the reaction mixture comprising the at least one complex of at least one nucleophilic polymeric carbanion (P- ) and at least one metal cation (M+) with at least one coupling agent (C) and optionally at least one terminating agent (T), to obtain a polymer product (P1). When at least one terminating agent (T) is used, the reaction mixture may be combined with the at least one coupling agent (C) and the at least one terminating agent (T) in any order, provided that the order, type and amount of the at least one coupling agent (C) and of the at least one terminating agent (T) is selected, so that a portion of the polymeric carbanion (P-) reacts with the at least one coupling agent (C) to form coupled polymer chains (P-P) and a portion of the polymeric carbanion (P-) reacts with the at least one coupling agent (C) and / or the at least one terminating agent (T) to form terminated polymer chains (P).

[0030] For example, the at least one terminating agent (T) may be added to the reaction mixture before the at least one coupling agent (C), after the at least one coupling agent (C) or simultaneously with the at least one coupling agent (C). Moreover, the at least one coupling agent (C) and / or the at least one terminating agent (T) may be added to the reaction mixture in a single portion, in several portions or continuously, or the reaction mixture may be added to the at least one coupling agent (C), the at least one terminating agent (T) or a mixture thereof.

[0031] The at least one coupling agent (C) may be any compound that is capable of reacting with at least two molecules of nucleophilic polymeric carbanion (P-), forming covalent bonds with both and resulting in coupled polymer chains (P-P). Accordingly, the at least one coupling agent (C) has a functionality fcof at least 2, preferably 2 to 4, more preferably 2 to 3, more preferably 2, where the functionality fcdefines the maximum number of nucleophilic polymeric carbanion (P-) molecules that can be coupled together by the coupling agent (C) to form coupled polymer chains (P-P).

[0032] Suitable coupling agents (C) may be, e.g. organic compounds comprising two or more functional groups that can react with a nucleophilic polymeric carbanion (P-), or compounds comprising functional groups that can react with two or more molecules of nucleophilic polymeric carbanions (P-), by forming a covalent bond therewith. For example, coupling agents (C) 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 carbanions (P-). 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 (C), since the carbonyl group of these compounds may react two or more times with nucleophilic polymeric anions (P-).

[0033] Preferably, the coupling agent (C) comprises

[0034] A) at least one, preferably one group (F1) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a reaction cascade comprising a nucleophilic addition reaction, an elimination of a leaving group and a further nucleophilic addition reaction;

[0035] B) at least two, preferably two groups (F2) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic addition or substitution reaction thereby each forming an anionic moiety within the formed terminated polymer chain (Pc), wherein the at least two groups (F2) are preferably located at a distance to each other of not more than 10, preferably not more than 6, more preferably not more than 3 covalent bonds;

[0036] C) at least two, preferably two groups (F3) capable of being substituted by the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic substitution reaction, preferably SN1 reaction, wherein the at least two groups (F3) are preferably located at a distance to each other of not more than 4, preferably not more than 2 covalent bonds;

[0037] D) a combination of at least two groups selected from (F1), (F2) and (F3), wherein the at least two groups are preferably located at a distance to each other of not more than 10, preferably not more than 6, more preferably not more than 3 covalent bonds.

[0038] More preferably, the coupling agent (C) comprises functional groups selected from ester groups, halogenated hydrocarbon groups, epoxide groups, acrylate groups and methacrylate groups. More preferably, the coupling agent (C) is a carboxylic acid ester, more preferably a carboxylic acid alkyl ester, more preferably an alkyl acetate, more preferably ethyl acetate.

[0039] The optional at least one terminating agent (T) may be any terminating 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, thus forming terminated polymer chains (P) without forming coupled polymer chains (P- P).

[0040] For example, terminating agents (T) may be selected from compounds that transfer a proton or other cationic group (such as a Lewis-acid) to the nucleophilic polymeric carbanion (P-), thereby forming terminated polymer chains (P), or compounds that transfer a non-cationic group to the nucleophilic polymeric carbanion (P-), thereby forming a salt of at least one anionic precursor of the terminated polymer chains (P) and at least one metal cation (M+).

[0041] Suitable terminating agents (T) that transfer a proton to the nucleophilic polymeric carbanion (P-), thereby forming terminated polymer chains (P), include water, alcohols, amines, thiols and other Bronsted acids that have a lower acid constant (PKA) than the protonated form of the polymeric carbanion (P-). Certain terminating agents (T) may also transfer multiple protons to multiple molecules of nucleophilic polymeric carbanion (P-), such as organic polyols having more than one hydroxyl group, e.g. glycols. However, terminating agents (T) that transfer a single proton to a single molecule of nucleophilic polymeric carbanion (P-) are preferred.

[0042] Suitable terminating agents (T) that transfer other cationic groups to the nucleophilic polymeric carbanion (P-), thereby forming terminated polymer chains (P) include, e.g., tri- organyl oxonium, triorganyl sulfonium or carbenium salts, which transfer an organyl cation to the nucleophilic polymeric carbanion (P-), or halogenated organic compounds, which may undergo nucleophilic substitution and / or transfer a halonium cation to the nucleophilic polymeric carbanion (P-).

[0043] Suitable terminating agents (T) that transfer a non-cationic group to the nucleophilic polymeric carbanion (P-), thereby forming a salt of at least one anionic precursor of the terminated polymer chains (P) and at least one metal cation (M+), include ethers (which react with carbanions at elevated temperatures), preferably cyclic ethers, more preferably epoxides and carbonyl compounds, such as ketones or aldehydes. While some of these compounds may further polymerize under suitable conditions, e.g. formaldehyde, which may form polyoxymethylene, or cyclic ethers, 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.

[0044] Preferably, the terminating agent (T) is selected from the group consisting of alcohols, and water, more preferably from the group consisting of methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol and water, more preferably from the group consisting of iso-propanol and water.

[0045] The at least one coupling agent (C) and the optional terminating agent (T) are used in amounts satisfying the following condition fc ■ n(C) + n(T) > n(p-), wherefcis the functionality of the coupling agent, n(P") is the molar amount of nucleophilic polymeric carbanions (P-) used in step ii), n(C) is the molar amount of the at least one coupling agent (C) used in step ii), and n(T) is the molar amount of the optional at least one terminating agent (T) used in step ii).

[0046] Where multiple coupling agents with different functionalities are used, the product fc■ n(C) is calculated for each individual coupling agent, thus that fc■ n(C) is expressed by where m is the number of different coupling agents with different functionalities and fciis the functionality of the jthcoupling agent q and n( ) is the molar amount of the jthcoupling agent q.

[0047] The at least one coupling agent (C) and the optional at least one terminating agent (T), as well as their amounts and the order in which they are combined with the at least one nucleophilic polymeric carbanion (P-) are selected, thus that a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) to form coupled polymer chains (P-P) and a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) and / or the at least one terminating agent (T) to form terminated polymer chains (P), where the terminated polymer chains (P) comprise polymer chains (Pc) that were terminated by the at least one coupling agent (C) and / or polymer chains (PT) that were terminated by the at least one terminating agent (T). Accordingly, the polymer product (P1) obtained in step ii) comprises a mixture of terminated polymer chains (P) and coupled polymer chains (P-P).

[0048] For example, in order to obtain a mixture of terminated polymer chains (P) and coupled polymer chains (P-P) in the polymer product (P1), the at least one coupling agent (C) and the optional at least one terminating agent (T), as well as their amounts and the order in which they are combined with the at least one nucleophilic polymeric carbanion (P-) can be selected to satisfy at least one of the following conditions: a) fc■ n(C) > n(P~) > n(C) and preferably a1) a rate-determining reaction step is interposed after the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the nucleophilic polymeric carbanion (P-) and before the reaction of the resultant terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-); and / or a2) the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the at least one nucleophilic polymeric carbanion (P-) is kinetically favoured over the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-); b) fc■ n(C) > n(P~) and only a portion (Ci) of the coupling agent (C) is combined with the at least one nucleophilic polymeric carbanion (P-), where n( ) is the molar amount of said portion, and wherein fc■ n(C, ) < n(P"), and the resultant product mixture is combined with the remainder of the coupling agent (C) after the reaction of the at least one nucleophilic polymeric carbanion (P-) with the portion (Ci) of the coupling agent (C) to form coupled polymer chains (P-P) is at least partially, preferably fully, completed; c) fc■ n(C) < n(P~) and n(T) > n(P~) - fc■ n(Cf, and preferably c1) the coupling agent (C) is combined with the at least one nucleophilic polymeric carbanion (P-), and the resultant product mixture is combined with the terminating agent (T) after the reaction of the at least one nucleophilic polymeric carbanion (P-) with the coupling agent (C) to form coupled polymer chains (P-P) is at least partially, preferably fully, completed; and / or c2) the reaction of the at least one nucleophilic polymeric carbanion (P-) with the at least one terminating agent (C) to form coupled polymer chains (P-P) is kinetically favoured over its reaction with the at least one terminating agent (T) to form terminated polymer chains (PT); d) at least a portion of the at least one terminating agent (T) is combined with the nucleophilic polymeric carbanion (P-) before the at least one coupling agent (C), where nflf) is the molar amount of the terminating agent (T) combined with the nucleophilic polymeric carbanion (P-) before the at least one coupling agent (C), and wherein nflf) < n(P~f, and preferably d1) fc ’ n(C) n(P") - wherein if fc■ n(C) < n(P~) - nflf), a second portion of the at least one terminating agent (T) is added in an amount sufficient to terminate any residual amount of polymeric carbanion (P-); and / or d2) the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-) to form coupled polymer chains (P-P) is kinetically favoured over the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the nucleophilic polymeric carbanion (P-) to form a terminated polymer chain (Pc); and / or d3) fc■ n(C) > n P~) - nflf) > n(Cf, e) at least a portion of the at least one terminating agent (T) is combined with the nucleophilic polymeric carbanion (P-) together with the at least one coupling agent (C), and wherein the reaction of the at least one nucleophilic polymeric carbanion (P-) with the at least one terminating agent (T) is kinetically preferred over its reaction with the at least one coupling agent (C), where nflf) is the molar amount of the terminating agent (T) combined with the nucleophilic polymeric carbanion (P-) together with the at least one coupling agent (C), and wherein nflf) < n(P~y, and preferably e1) fc ’ n(C) n(P") - nfjf), wherein if fc■ n(C) < n(P~) - nflf), a second portion of the at least one terminating agent (T) is added in an amount sufficient to terminate any residual amount of polymeric carbanion (P-); and / or e2) the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-) to form coupled polymer chains (P-P) is kinetically favoured over the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the nucleophilic polymeric carbanion (P-) to form a terminated polymer chain (Pc); and / or e3) fc■ n(C) > n(P~) - nflf) > n(Cf

[0049] The conditions a) to e) are explained in the following in more detail.

[0050] Condition a) By satisfying the term n(P") > n(C) of condition a), it is possible to make a portion of the coupling agent (C) react with more than one molecule of nucleophilic polymeric carbanion (P-), thereby forming coupled polymer chains (P-P), and to prevent exclusive formation of terminated polymer chains (P).

[0051] At the same time, by satisfying the term fc■ n(C) > n(P~) of condition a), it is possible to terminate the living anionic polymerization reaction without the need for further terminating agent (T), and to make all molecules of the nucleophilic polymeric carbanion (P-) that were not coupled to form coupled polymer chains (P-P) react with the coupling agent (C) to form coupling agent-terminated polymer chains (Pc).

[0052] By satisfying the optional additional conditions a1) and / or a2) of condition a), it is possible to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (Pc).

[0053] Such reaction control can be achieved by varying the reaction conditions, such as temperature and the selection of solvent, or by selection of specific types of coupling agents that satisfy the optional conditions a1) and / or a2).

[0054] Suitable coupling agents satisfying the optional condition a1), wherein a rate-determining reaction step is interposed after the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the nucleophilic polymeric carbanion (P-) and before the reaction of the resultant terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-), include, e.g. coupling agents (C) comprising at least one, preferably one group (F1) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a reaction cascade comprising a nucleophilic addition reaction, an elimination of a leaving group and a further nucleophilic addition reaction.

[0055] Such coupling agents (C) include, e.g. carboxylic acid derivatives, such as carboxylic acid esters, amides, anhydrides, imides, acyl chlorides, lactones and lactams, preferably carboxylic acid esters, more preferably carboxylic acid alkyl esters, more preferably alkyl acetates, more preferably ethyl acetate. In such coupling agents, elimination of the leaving group will typically be a rate-determining step between the two nucleophilic addition reactions between the carbonyl group of the group (F1) and the molecules of a nucleophilic polymeric carbanion (P-), thus that the formation of coupling agent-terminated polymer chains (Pc) occurs faster than the formation of coupled polymer chains (P-P).

[0056] Suitable coupling agents satisfying the optional condition a2), wherein the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the at least one nucleophilic polymeric carbanion (P-) is kinetically favoured over the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-), include, e.g., coupling agents (C) comprising a functional group (F2) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic addition or substitution reaction thereby each forming an anionic moiety within the formed terminated polymer chain (Pc), wherein the functional group (F2) is located in proximity to a second functional group (F), preferably at a distance of not more than 10, preferably not more than 6, more preferably not more than 3 covalent bonds. Such coupling agents (C) may include, e.g., carbonyl groups (including carboxyl groups) or epoxide groups.

[0057] For example, where the coupling agent (C) comprises a carbonyl group in proximity to a second functional group (F), the carbonyl group may react with a first molecule of the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic addition reaction, thereby forming a coupling agent-terminated polymer chain (Pc) comprising a negatively charged alcoholate group, which leads to electronic repulsion from further molecules of nucleophilic polymeric carbanion (P-). Similarly, where the coupling agent (C) comprises an epoxide group in proximity to a second functional group (F), the epoxide group may react with a first molecule of the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic substitution reaction, thereby forming a coupling agent-terminated polymer chain (Pc) comprising a negatively charged alcoholate group, which leads to electronic repulsion from further molecules of nucleophilic polymeric carbanion (P-).

[0058] Thus, the reaction of another molecule of the coupling agent (C) with further molecules of nucleophilic polymeric carbanion (P-) becomes kinetically favoured over the reaction of the second functional group (f) of the formed coupling agent-terminated polymer chain (Pc) with further molecules of nucleophilic polymeric carbanion (P-).

[0059] Further suitable coupling agents satisfying the optional condition a2), wherein the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the at least one nucleophilic polymeric carbanion (P-) is kinetically favoured over the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-), include, e.g., coupling agents (C) comprising a groups (F3) capable of being substituted by the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic substitution reaction, wherein the group (F3) is located in proximity to a second functional group (F), preferably at a distance of not more than 4, preferably not more than 2 covalent bonds.

[0060] For example, the coupling agent (C) may comprise a hydrocarbon moiety comprising an anionic leaving group (F3), such as a halide or pseudohalide group, in proximity to a second functional group (F). Such moiety may react with a first molecule of the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic substitution reaction, thereby forming a coupling agent- terminated polymer chain (Pc) comprising a sterically encumbered moiety, which leads to steric repulsion from further molecules of nucleophilic polymeric carbanion (P-).

[0061] Thus, the reaction of another molecule of the coupling agent (C) with further molecules of nucleophilic polymeric carbanion (P-) becomes kinetically favoured over the reaction of the second functional group (F) of the formed coupling agent-terminated polymer chain (Pc) with further molecules of nucleophilic polymeric carbanion (P-).

[0062] Such kinetic control is typically more pronounced in cases where the anionic leaving group is already present at a sterically encumbered position, e.g. in secondary or tertiary alkyl halides, which tend to react in SN1 nucleophilic substitution reactions. Accordingly, the group (F3) is preferably capable of being substituted by the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic SN1 reaction.

[0063] Condition b)

[0064] By combining only a portion (Ci) of the coupling agent (C) with the at least one nucleophilic polymeric carbanion (P-), thus that fc■ n( ) < n(P"), and allowing said portion (Ci) to react with the at least one nucleophilic polymeric carbanion (P“),it is possible to make the portion of the coupling agent (Ci) partly or entirely react with more than one molecule of nucleophilic polymeric carbanion (P-), thereby forming coupled polymer chains (P-P), and to prevent exclusive formation of terminated polymer chains (P).

[0065] At the same time, by satisfying the term fc■ n(C) > n(P~) of condition b), it is possible to terminate the living anionic polymerization reaction without the need for further terminating agent (T), and to make all molecules of the nucleophilic polymeric carbanion (P-) that were not coupled to form coupled polymer chains (P-P) react with the coupling agent (C) to form coupling agent-terminated polymer chains (Pc).

[0066] By satisfying condition b), it is no longer necessary to satisfy the term n(P") > n(C) or any of the optional conditions a1) or a2) described for condition a), since the formation of both coupled polymer chains (P-P) and terminated polymer chains (P) is enabled by portion-wise use of the coupling agent (C).

[0067] For example, a molar surplus of coupling agent (C) can be used overall, thus that n(C) > n(P"), and kinetic control of the reaction by selecting appropriate reactivity of the coupling agent or appropriate reaction conditions is not necessary, since reaction control is achieved by portion-wise combination of the coupling agent (C) with the nucleophilic polymeric carbanion (P-).

[0068] Condition c)

[0069] By satisfying the term fc■ n(C) < n(P~) of condition c), it is possible to prevent exclusive formation of coupled polymer chains (P-P) without the formation of terminated polymer chains (P). In this case, the stoichiometry dictates that a portion of the nucleophilic polymeric carbanion (P-) does not react with a coupling agent (C).

[0070] At the same time, by satisfying the term n(T) > n(P") - fc- n(C) of condition c), it is possible to ensure that all molecules of nucleophilic polymeric carbanion (P-) are coupled or terminated at the end of the reaction.

[0071] By satisfying the optional additional conditions c1) and / or c2) of condition c), it is possible to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (P).

[0072] By satisfying optional condition c1), i.e. by combining the coupling agent (C) with the at least one nucleophilic polymeric carbanion (P-), thus thatfc■ n(C) < n(P"), and allowing the coupling agent (C) to react with the at least one nucleophilic polymeric carbanion (P- ) before adding the terminating agent (T), it is possible to make the coupling agent (C) partly or entirely react with more than one molecule of nucleophilic polymeric carbanion (P-), thereby forming coupled polymer chains (P-P), and to prevent exclusive formation of terminated polymer chains (P).

[0073] By satisfying condition c1), the formation of both coupled polymer chains (P-P) and terminated polymer chains (P) is enabled by the stoichiometry according to condition c) and by subsequent use of the coupling agent (C) and the terminating agent (T).

[0074] Preferably, a molar surplus of terminating agent (T) is used overall, thus that n(T) > n(P~). Kinetic control of the reaction by selecting appropriate reactivity of the coupling agent or appropriate reaction conditions is not necessary, since reaction control is achieved by stoichiometry and subsequent use of the coupling agent (C) and the terminating agent (T).

[0075] By satisfying optional condition c2), wherein the reaction of the at least one nucleophilic polymeric carbanion (P-) with the at least one terminating agent (C) to form coupled polymer chains (P-P) is kinetically favoured over its reaction with the at least one terminating agent (T) to form terminated polymer chains (PT), it is possible to purposefully prevent exclusive formation of terminated polymer chains (P) and / or to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (PT), even if the coupling agent (C) and the terminating agent (T) are combined with the at least one nucleophilic polymeric carbanion (P-) simultaneously.

[0076] Such reaction control can be achieved by varying the reaction conditions, such as temperature and the selection of solvent, or by selection of specific types of coupling agents (C) and terminating agents (T).

[0077] For example, it is possible to combine the at least one nucleophilic polymeric carbanion (P-) simultaneously with a coupling agent (C) that readily reacts with nucleophilic carbanions, such as any of the coupling agents described above, and with a terminating agent (T), whose reaction with nucleophilic carbanions is slow or kinetically hindered compared to the reaction of the coupling agent (C).

[0078] Such terminating agents (T) may, e.g. include heteroatom-containing hydrocarbons, such as ethers, in particular dialkyl ethers and / or tetra hydrofuran, which tend to slowly undergo alpha-deprotonation and further degradation when exposed to nucleophilic carbanions at sufficiently high temperatures. Further such terminating agents (T) may include substituted aromatic compounds, which tend to slowly undergo deprotonation of sp2C-H bonds at sufficiently high temperatures or in the presence of coordinating solvents, whose C-H bond acidity may be controlled by the substitution pattern of the aromatic ring. Further such terminating agents (T) may include aryl alkanes, which tend to slowly undergo deprotonation of the C-H bond in the alpha-position relative to the aryl group at sufficiently high temperatures or in the presence of coordinating solvents, whose C-H bond acidity may be controlled by the substitution pattern of the aromatic ring.

[0079] Further, such terminating agents (T) may include sterically encumbered electrophilic compounds.

[0080] Condition d)

[0081] By combining at least a portion (Ti) of the at least one terminating agent (T) with the nucleophilic polymeric carbanion (P-) before the at least one coupling agent (C), provided the molar amount of said portion of the at least one terminating agent (T) is smaller than the molar amount of the nucleophilic polymeric carbanion (P-) (i.e. n^Ti) it is possible to ensure that only a portion of the nucleophilic polymeric carbanion (P-) reacts with the terminating agent (T) to form terminated polymer chains (PT) leaving the remainder of the nucleophilic polymeric carbanion (P-) active and open to reaction with the subsequently added coupling agent (C). By satisfying the optional additional conditions d1), d2) and / or d3) of condition d), it is possible to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (Pc).

[0082] By satisfying condition d1), fc■ n(C) < n P~) - nfiT , it is possible to make substantially all of the coupling agent (C) react with the at least one nucleophilic polymeric carbanion (P-), forming coupled polymer chains (P-P). If any molecules of nucleophilic polymeric carbanion remain after this step, these may be terminated e.g. by addition of a remainder of the terminating agent (T), which was not used as part of the portion (Ti).

[0083] By satisfying condition d2), wherein the reaction of a terminated polymer chain (Pc) with a second molecule of a nucleophilic polymeric carbanion (P-) to form coupled polymer chains (P-P) is kinetically favoured over the reaction of a molecule of the at least one coupling agent (C) with a first molecule of the nucleophilic polymeric carbanion (P-) to form a terminated polymer chain (Pc), it is possible to purposefully prevent exclusive formation of terminated polymer chains (Pc) from the remainder of the at least one nucleophilic polymeric carbanion (P-) and / or to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (Pc).

[0084] Such reaction control can be achieved by varying the reaction conditions, such as temperature and the selection of solvent and by selection of specific types of coupling agents (C).

[0085] For example, the remainder of the at least one nucleophilic polymeric carbanion (P-) could be combined with a coupling agent (C) that comprises two leaving groups attached to the same carbon atom, each capable of being substituted by a molecule of the at least one nucleophilic polymeric carbanion (P-), under conditions that favour the second nucleophilic substitution.

[0086] For example, the reaction conditions may be selected to be more favourable for SN1 reactions, and less favourable for SN2 reactions (e.g. by increasing temperature and polarity of the solvent), whereas the coupling agent may be selected to be more susceptible to SN2 reactions than to SN1 reactions, as is e.g. the case for terminal (i.e. primary) leaving groups. In such case, the first nucleophilic substitution reaction (SN2) of the primary leaving group can generate a terminated polymer chain (Pc), where the other leaving group becomes a secondary leaving group due to the presence of the added polymer chain, making the terminated polymer chain (Pc) more susceptible to SN1 reactions. Due to the selection of the reaction conditions in favour of SN1 reactions, the first reaction should be slower than the second reaction in such reaction setup. By satisfying condition d3), wherein fc■ n(C) > n P~) - n(7 ) > n(C), it is possible to avoid a need for addition of further terminating agent (T) for termination of residual polymeric carbanion (P-), since the amount of coupling agent (C) having the functionality fcis sufficient for coupling and termination of all residual polymeric carbanion (P-) not terminated by the amount of terminating agent (T) initially added under condition d). At the same time, by satisfying n(P") - n T > n(C) exclusive formation of terminated polymer chains (Pc) from the residual polymeric carbanion (P-) can be purposefully avoided.

[0087] Condition e)

[0088] Moreover, it is possible to combine at least a portion (Ti) of the at least one terminating agent (T) with the nucleophilic polymeric carbanion (P-) simultaneously with the at least one coupling agent (C), in order to obtain a desired mixture of terminated polymer chains (P) and coupled polymer chains (P-P), provided the molar amount of said portion (Ti) of the at least one terminating agent (T) is smaller than the molar amount of the nucleophilic polymeric carbanion (P-) (i.e. n^Ti) and provided the reaction of the at least one nucleophilic polymeric carbanion (P-) with the at least one terminating agent (T) is kinetically preferred over its reaction with the at least one coupling agent (C). By satisfying the term n^Ti) < n(P~), exclusive formation of terminated polymer chains (PT) is avoided, since a portion of active nucleophilic polymeric carbanion (P-) remains.

[0089] Terminating agents (T) suitable for satisfying condition e) involve any terminating agents that react with nucleophilic carbanion more readily than the selected coupling agent. For example such terminating agents may be selected from alcohols and other proton donors, which readily transfer a proton to nucleophilic carbanions, electrophiles, which readily react with nucleophilic carbanions in nucleophilic addition reactions, and halogenated hydrocarbons which undergo metal-halogen exchange when exposed to complexes of nucleophilic carbanions and metal cations.

[0090] By satisfying the optional additional conditions e1), e2) and / or e3) of condition e), it is possible to control the extent of formation of coupled polymer chains (P-P) and terminated polymer chains (Pc). These optional conditions correspond to the conditions d1), d2) and d3), respectively, and serve the corresponding purposes.

[0091] Preferably, the method of the invention involves combining the at least one nucleophilic polymeric carbanion (P-) with the at least one coupling agent (C), in order to obtain a reaction mixture comprising coupled polymer chains (P-P) and optionally coupling-agent- terminated polymer chains (Pc), and the obtained reaction mixture is subsequently combined with a terminating agent (T), to generate a mixture comprising coupled polymer chains (P-P), and terminated polymer chains (P), which include coupling-agent-termi- nated polymer chains (Pc), terminating-agent-terminated polymer chains (PT) or both. Accordingly, the terminating agent (T) is preferably combined with the at least one nucleophilic polymeric carbanion (P-) after the reaction of the at least one nucleophilic polymeric carbanion (P-) with the coupling agent (C) to form coupled polymer chains (P-P) is at least partially, preferably fully, completed.

[0092] Often, the terminating agent (T) will also react with any reactive moieties of the coupling- agent-terminated polymer chains (Pc) and coupled polymer chains (P-P), making these polymer chains more suited for further processing. This will typically be the case where the terminating agent (T) is a proton donor, such as an alcohol or water, and where the coupling-agent-terminated polymer chains (Pc) and coupled polymer chains (P-P), are anionic after the reaction between the at least one nucleophilic polymeric carbanion (P- ) with the at least one coupling agent (C). Therefore, a terminating agent (T) is preferably added to the reaction mixture even if no active molecules of nucleophilic polymeric carbanion (P-) are present after the reaction with the at least one coupling agent (C).

[0093] In cases, where the reaction between the at least one nucleophilic polymeric carbanion (P-) with the at least one coupling agent (C) generates both coupled polymer chains (P-P) and terminated polymer chains (Pc), the generation of terminated polymer chains (Pc) may be a result of different effects or reactions. On the one hand, in cases where fc■ n(C) > n(P~), terminated polymer chains (Pc) having a functionality fPcof fc- 1 will be generated due to stoichiometry. On the other hand, terminated polymer chains (Pc) may be generated by side-reactions, e.g. deprotonation of the coupling agent (C) or a terminated polymer chain (Pc) by the at least one nucleophilic polymeric carbanion (P-).

[0094] For example, where alkyl carboxylates are used as coupling agent (C), the reaction of the at least one nucleophilic polymeric carbanion (P-) with the at least one coupling agent (C) may lead to reactions shown in the following Scheme 1 (showing examples of reactions with ethyl acetate as coupling agent (C)) and similar reactions, where (Pc-i) represents a terminated polymer chain (Pc) having a functionality fPcof fc- 1; (Pc-n) represents a terminated polymer chain (Pc) obtained from a nucleophilic polymeric carbanion (P-) by deprotonation of the terminated polymer chain (Pc-i); and (Pc-m) represents a terminated polymer chain (Pc) obtained from a terminated polymer chain (Pc-i) through deprotonation by a nucleophilic polymeric carbanion (P-), and where R is a group corresponding to the polymer chain of (P-).

[0095] In step i) of the method of the invention, the polymerization of the at least one monomer (A) is preferably carried out until the peak molecular weight Mp Pof the nucleophilic polymeric carbanion (P-) is in the range of from 50 to 150 kg / mol, more preferably from 60 to 120 kg / mol, more preferably from 65 to 100 kg / mol, more preferably from 70 to 80 kg / mol. The peak molecular weight can be determined by gel permeation chromatography calibrated to polystyrene standards after protonation of a sample of the nucleophilic polymeric carbanion (P-) using propan-2-ol.

[0096] The peak molecular weight Mp Pof the nucleophilic polymeric carbanion (P-) is the molecular weight, at which the molecular weight distribution shows the highest intensity. Accordingly, if the molecular weight distribution of the nucleophilic polymeric carbanion (P-) contains a single peak, the peak molecular weight Mp Pis determined from the single peak, whereas if the molecular weight distribution of the nucleophilic polymeric carbanion (P-) contains multiple peaks, the peak molecular weight Mp Pis determined from the highest peak. Typically, the molecular weight distribution of the nucleophilic polymeric carbanion (P-) will have a single peak, unless reaction conditions are selected that purposefully lead to multimodal distributions (e.g. addition of further initiator during anionic polymerization).

[0097] In step ii) of the method of the invention, the amount of the coupling agent (C) is preferably selected thus that the ratio is in the range of from 0.1 to 1.5, preferably from 0.2 to 1.2, more preferably from 0.3 to 1.1 , more preferably from 0.5 to 1.0. The molar amount n(P") of nucleophilic polymeric carbanions (P-) present in step ii) will typically essentially correspond to the molar amount of initiator (I) used in step i).

[0098] Typically, the weight average molecular weight Mw P1of the polymer product (P1) obtained in step ii), determined by gel permeation chromatography calibrated to polystyrene standards, will be in the range of 1.20 ■ Mw P< Mw P1< 1.99 ■ Mw P, often 1.49 ■ Mw P< Mw P1< 1.98 ■ Mw P, such as 1.75 ■ Mw P< Mw P1< 1.95 ■ Mw P, for example 1.90 ■ Mw P< Mw P1< 1.93 ■ Mw P, wherein Mw Pis the weight average molecular weight of the nucleophilic polymeric carbanion (P-) determined before the reaction with the coupling agent (C) by gel permeation chromatography calibrated to polystyrene standards after protonation of a sample of the nucleophilic polymeric carbanion (P-) using propan- 2-ol.

[0099] Where the ranges specified above are applied, the polymer product (P1) obtained in step ii) will typically have a peak molecular weight Mp P1, determined by gel permeation chromatography calibrated to polystyrene standards, in the range of from 100 to 200 kg / mol, often 135 to 180 kg / mol, for example 140 to 150 kg / mol, which have a particularly beneficial balance of softness and dimensional stability, especially when compared with polymers having a similar processability, which were prepared by unidirectional living anionic polymerization and have a similar polymer block structure.

[0100] The peak molecular weight Mp P1of the polymer product (P1) in the present context is the molecular weight, at which the molecular weight distribution shows the highest intensity that can be attributed to the coupled polymer chains (P-P), or, if only a single peak can be detected, the molecular weight at which the overall molecular weight distribution shows the highest intensity. Accordingly, if the molecular weight distribution of the polymer product (P1) contains a single distinct peak, the peak molecular weight Mp P1is determined from the single distinct peak, whereas if the molecular weight distribution of the polymer product (P1) contains multiple peaks, the peak molecular weight Mp P1is determined from the highest peak that can be attributed to the coupled polymer chains (P-P). Typically, peaks are attributed to the coupled polymer chains (P-P) if they are at a substantially different molecular weight than those determined for the nucleophilic polymeric carbanion (P-) (e.g. at least 1.5 times Mp P).

[0101] Typically, the molecular weight distribution of the polymer product (P1) will have two distinct peaks, one of which can be attributed to the terminated polymer chains (P), which will essentially correspond to Mp P, and one of which can be attributed to coupled polymer chains (P-P), thus defining Mp P1, unless reaction conditions are selected that purposefully lead to multimodal distributions (e.g. addition of further initiator during anionic polymerization).

[0102] Therefore, in some preferred embodiments of the method of the invention, the method described above is for the preparation of a polymer product (P1) with lower Shore hardness, higher Vicat softening temperature or a combination thereof compared with a reference polymer product (P2) having a target melt volume rate. In such embodiments, the method comprises the steps:

[0103] I) selecting a reference polymer product (P2) having a target melt volume rate MVRP2, and further having a peak molecular weight Mp P2, a Vicat softening temperature VSTP2and a Shore hardness SHP2, wherein the polymer product (P2) is obtained by linear unidirectional anionic polymerization terminated in the absence of a coupling agent, and has a linear, essentially symmetrical structure;

[0104] II) carrying out the method described above, wherein following conditions apply: a) in step i), the anionic polymerization of the at least one monomer (A) is carried out in a monomer sequence corresponding to the monomer sequence of the polymer product (P2) from one terminal end of polymer product (P2) to the centre of polymer product (P2); b) in step i), the anionic polymerization of the at least one monomer (A) is carried out up to a peak molecular weight Mp P, which satisfies the condition 0.4 ■ Mp P2 — Mp P< 0.8 ■ Mpp2, c) in step ii), a coupling agent (C) having a functionality fcof 2 is used, and a polymer product (P1) with a peak molecular weight Mp P1is obtained, which satisfies the condition 1.8 ■ Mp P< Mp P1< 2.2 ■ Mp P, to obtain a polymer product (P1) having a melt volume rate MVRP1, a Vicat softening temperature VSTP1and a Shore hardness SHP1, wherein the melt volume rate MVRP1of the obtained polymer product (P1) deviates by not more than 40% from the target melt volume rate MVRP2, and wherein, VSTP1> VSTP2, and / or SHP1< SHP2.

[0105] In step I), the reference polymer product (P2) may be any polymer product obtained by linear unidirectional anionic polymerization that has a linear, essentially symmetrical structure. In the context of the present invention, the expression “linear unidirectional anionic polymerization” describes living anionic polymerization, which is carried out by providing an anionic polymerization initiator, e.g. the at least one anionic polymerization initiator (I) as described above, and a sequence of monomers, e.g. the at least one monomer (A) as described above, wherein termination of the anionic polymerization does not involve the use of a coupling agent.

[0106] The expression “essentially symmetrical structure” in the context of polymers obtained by linear unidirectional anionic polymerization means that the polymer comprises only a single block of repeating units, or is a block copolymer comprising a central block of repeating units, wherein the sequence of repeating units within the polymer starting from the organic residue derived from the initiator to the central block is repeated in reversed order starting from the central block of the polymer to the terminal end resulting from termination of the living anionic polymerization. “Essentially symmetrical structure” in the present context does not imply full mirror-symmetry, since the polymer will deviate from having mirror-symmetry due to statistical effects, due to different terminal ends (resulting from initiation vs. termination) and potentially due to preferred orientation of individual monomers (e.g. styrene) or preferred polymerization of different types of monomers (e.g. tapered blocks).

[0107] Accordingly, the reference polymer product (P2) is obtained by polymerizing a single monomer or mixture of monomers, to form a single block of repeating units, or by polymerizing a first sequence of monomers to obtain a sequence of repeating units within the polymer starting from the organic residue derived from the initiator to the central block, polymerizing a single monomer or mixture of monomers, to form a central block of repeating units, and polymerizing a second sequence of monomers to obtain a sequence of repeating units starting from the central block of repeating units to the terminal end resulting from termination of the living anionic polymerization, wherein the second sequence of monomers corresponds to the first sequence of monomers in reverse.

[0108] The reference polymer product (P2) can be selected, e.g. based on a particular product having desired properties, in particular desired melt volume rate MVRP2, but e.g. having insufficiently low shore hardness SHP2and / or insufficiently high Vicat softening temperature VSTP2.

[0109] Such polymer product will typically have a specific monomer and block sequence and a specific molecular weight distribution, including a peak molecular weight MP)P2leading to the desired properties. In step II), the method described above as described above is carried out, thus that in step i), the anionic polymerization of the at least one monomer (A) is carried out in a monomer sequence corresponding to the monomer sequence of the polymer product (P2) from one terminal end of polymer product (P2) to the centre of polymer product (P2).

[0110] This means that in step i) either half of the amount of the single monomer or mixture of monomers forming the single block of repeating units of reference product (P2) is polymerized, or a first sequence of monomers (A) is polymerized, which corresponds to the first sequence of monomers of the polymer product (P2), followed by polymerization of half of the amount of the single monomer or mixture of monomers used to form the central block of repeating units of the polymer product (P2).

[0111] Moreover, in step II), step i) of the method described above is carried out up to a peak molecular weight Mp P, which satisfies the condition 0.4 ■ Mp P2< Mp P< 0.8 ■ Mp P2, preferably 0.5 ■ Mp P2< Mp P< 0.75 ■ Mp P2, more preferably 0.55 ■ Mp P2< Mp P< 0.7 ■ Mp P2, more preferably 0.6 ■ Mp P2< Mp P< 0.7 ■ Mp P2.

[0112] Furthermore, in step II), the method described above is carried out thus that in step ii) a coupling agent (C) having a functionality fcof 2 is used to obtain a polymer product (P1) with a peak molecular weight Mp P1, which satisfies the condition 1.8 ■ Mp P< Mp P1< 2.2 ■ Mp P, preferably 1.9 ■ Mp P< Mp P1< 2.1 ■ Mp P, more preferably 1.95 ■ Mp P< Mp P1< 2.05 ■ Mp P, more preferably 1.95 ■ Mp P< Mp P1< 2 ■ Mp P.

[0113] The polymer product (P1) obtained in step II) will have a melt volume rate MVRP1, a Vicat softening temperature VSTP1and a Shore hardness SHP1, wherein the melt volume rate MVRP1of the obtained polymer product (P1) deviates by not more than 40%, often not more than 30%, such as not more than 20%, for example not more than 5% from the target melt volume rate MVRP2of the reference polymer product (P2). At the same time, the Vicat softening temperature of the polymer product (P1) will be greater than that of the reference polymer product (P2) (VSTP1> VSTP2) and / or the Shore hardness of the polymer product (P1) will be smaller than that of the reference polymer product (P2)

[0114] In a preferred embodiment, the method of the invention for the preparation of a polymer product (P1) by living anionic polymerization comprises the steps: i) performing anionic polymerization of at least one type of vinylaromatic monomer, preferably styrene, and at least one type of conjugated diene monomer, preferably butadiene, using at least one anionic polymerization initiator (I), which comprises an initiator complex of at least one nucleophilic alkyl carbanion (R-), preferably butyl (such as sec-butyl) carbanion and at least one metal cation (M+) selected from alkali metal and alkali earth metal cations, preferably Li+, to obtain a reaction mixture comprising at least one polymeric complex of at least one nucleophilic polymeric carbanion (P-) and the at least one metal cation (M+), with repeating units of the vinylaromatic monomer and the at least one type of conjugated diene monomer incorporated therein in a sequence of at least two polymer blocks with different monomer compositions, wherein the anionic polymerization is carried out until the peak molecular weight Mp Pof the nucleophilic polymeric carbanion (P-) is in the range of from 50 to 150 kg / mol, more preferably from 60 to 120 kg / mol, more preferably from 65 to 100 kg / mol, more preferably from 70 to 80 kg / mol, determined by gel permeation chromatography calibrated to polystyrene standards after protonation of a sample of the nucleophilic polymeric carbanion (P-) using pro- pan-2-ol; and ii) terminating the anionic polymerization by combining the reaction mixture, comprising at least one polymeric complex of at least one nucleophilic polymeric carbanion (P-) and at least one metal cation (M+), with at least one coupling agent (C) selected from alkyl carboxylates, preferably alkyl acetates, more preferably ethyl acetate, and optionally subsequently with at least one terminating agent (T), wherein in step ii) the amount of the coupling agent (C) is selected thus that the ratio is in the range of from 0.2 to 3, preferably from 0.4 to 2.4, more preferably from 0.6 to 2.2, more preferably from 1 .0 to 2.0, more preferably from 1 .5 to 1.7, to obtain a polymer product (P1), wherein the polymer product (P1) is a mixture of block copolymers, comprising terminated block copolymer chains (P) and coupled block copolymer chains (P-P), wherein the polymer product (P1) has a peak molecular weight, determined by gel permeation chromatography calibrated to polystyrene standards, in the range of from 100 to 200 kg / mol, preferably 135 to 180 kg / mol, more preferably 140 to 150 kg / mol, and wherein the weight average molecular weight Mw P1of the polymer product (P1 ) obtained in step ii), determined by gel permeation chromatography calibrated to polystyrene standards, is in the range of 1.20 ■ Mw P< Mw P1< 1.99 ■ Mw P, preferably 1.49 ■ Mw P< Mw P1< 1.98 ■ Mw P, more preferably 1.75 ■ Mw P< Mw P1< 1.95 ■ Mw P, more preferably 1.90 ■ Mw P< Mw P1< 1.93 ■ Mw P, wherein Mw Pis the weight average molecular weight of the nucleophilic polymeric carbanion (P-) determined before the reaction with the coupling agent (C) by gel permeation chromatography calibrated to polystyrene standards after protonation of a sample of the nucleophilic polymeric carbanion (P-) using propan- 2-ol.

[0115] Another aspect of the present invention is the polymer product (P1) obtained by the method according to the invention. Typically, the polymer product (P1) according to the present invention will have the properties described above for the polymer product (P1).

[0116] Preferably, the polymer product (P1) comprises from 1 to 60 wt-%, preferably from 5 to 50 wt-%, more preferably from 10 to 40 wt-%, more preferably from 15 to 30 wt-%, based on the total weight of terminated polymer chains (P) and coupled polymer chains (P-P), of terminated polymer chains (P) and from 40 to 99 wt-% by weight, more preferably from 70 to 90 wt-%, based on the total weight of terminated polymer chains (P) and coupled polymer chains (P-P), of coupled polymer chains (P-P).

[0117] Preferably, the polymer product (P1) has one or more, more preferably all of the following properties: a Shore (D) hardness, measured according to DIN EN ISO 868 - 2003-10 using a durometer, in the range of from 10 to 50, preferably from 20 to 40, more preferably from 25 to 35, more preferably from 27 to 33, and / or a Shore (A) hardness, measured according to DIN EN ISO 868 - 2003-10 using a durometer, in the range of from 40 to 120, preferably 45 to 110, more preferably 50 to 100, more preferably 70 to 95, more preferably 80 to 90; a Vicat softening temperature (A / 120), measured according to DIN EN ISO 306 - 2014- 03, in the range of from 30 to 60 °C, preferably from 35 to 50 °C, more preferably from 36 to 42 °C, wherein the coupled polymer chains (P-P) preferably comprise terminal blocks of vinylaromatic repeating units, or has a Vicat softening temperature (A / 50) measured according to DIN EN ISO 306 - 2014-03, in the range of from 20 to 50 °C, preferably 25 to 35 °C, more preferably 28 to 32 °C, wherein the coupled polymer chains (P-P) preferably comprise terminal blocks comprising conjugated diene and vinylaromatic repeating units; a melt volume rate measured at 200 °C under a load of 5 kg according to DIN ISO 1133- 1 :2012-03 in the range of from 5 to 30 cm3 / 10 min, preferably 10 to 20 cm3 / 10 min, more preferably from 11 to 17 cm3 / 10 min, more preferably 13 to 15 cm3 / 10 min; a peak molecular weight Mp P1, measured by gel permeation chromatography calibrated to polystyrene standards, in the range of from 100 to 200 kg / mol, preferably 135 to 180 kg / mol, more preferably from 140 to 150 kg / mol.

[0118] Preferably, the terminated polymer chains (P) in the polymer product (P1) comprise, preferably consist of, a sequence of a first polymer block and a second polymer block, wherein the repeating units in the first polymer block are aromatic vinyl repeating units, preferably styrene repeating units, and the repeating units in the second polymer block are conjugated diene repeating units, preferably butadiene repeating units, or a random or tapered mixture thereof with aromatic vinyl repeating units, preferably styrene repeating units, and the coupled polymer chains (P-P) in the polymer product (P1) comprise, preferably consist of, two said sequences coupled together by the coupling agent (C) via said second polymer block.

[0119] More preferably, the terminated polymer chains (P) have a block copolymer structure S- (S / B)r, and the coupled polymer chains (P-P) have a block copolymer structure S-(S / B)r- X-(S / B)r-S, wherein S represents a block of styrene repeating units, wherein all blocks S have essentially the same length, (S / B)rrepresents a block of randomly or tapered copolymerized styrene and butadiene repeating units, wherein all blocks (S / B)rhave essentially the same length and X represents the coupling centre formed from the coupling agent (C), preferably a carboxylic acid alkyl ester, more preferably an alkyl acetate, more preferably ethyl acetate. “Essentially the same length” means that the respective block lengths may vary due to statistical effects of the polymerization process, despite being prepared by polymerizing the same monomer sequence.

[0120] More preferably, the amount of butadiene repeating units in the polymer product (P1) is in the range of from 20 to 50% by weight, preferably 25 to 45% by weight, more preferably 30 to 40% by weight, based on the total weight of repeating units in the polymer product (P1 ), and the amount of blocks represented by (S / B)ris in the range of from 50 to 80% by weight, more preferably from 55 to 75% by weight, more preferably from 60 to 72% by weight, more preferably from 65 to 70% by weight, based on the total weight of the polymer product (P1).

[0121] More preferably, the polymer product (P1) comprises polymer chains represented by following structure (P-PA) and polymer chains represented by one or more of following structures (PCA), (PCB) and / or (PTA): where R1is the organic residue of the initiator (I), preferably C1-C4 alkyl, more preferably n-butyl, iso-butyl, sec-butyl or tert-butyl; R2is the organic residue of the carboxylic acid part of a carboxylic acid ester, preferably C1-C4 alkyl, more preferably methyl; R3is the organic residue of the alcohol part of a carboxylic acid ester, preferably C1-C4 alkyl, more preferably ethyl; b indicates a transition between two polymer blocks and r indicates a random or tapered distribution of repeating units within a polymer block. The invention is further illustrated by the following examples and claims.

[0122] EXAMPLES

[0123] Melt volume rate (MVR) is measured at 200 °C with a 5 kg load according to DIN EN ISO 1133-1 :2022-10 using an Aflow Extrusion Plastometer (Zwick / Roell).

[0124] Shore A and Shore D hardness is measured according to DIN EN ISO 868 - 2003-10, using a durometer, on sample plaques having a thickness of 6 mm for the duration of 15 s. The samples were produced by injection molding using an Arbug 320 S injection molding machine at 200 °C, a rotational speed of 300 rpm, an injection speed of 4 cm3 / s, an injection pressure of 1500 bar and a cooling time of 50 s at 25 °C. The samples were subsequently conditioned for 24 hours at 23 °C before measurements were made.

[0125] Molecular weight distributions, including peak molecular weights and weight average molecular weights are measured by gel permeation chromatography calibrated to polystyrene standards, where applicable after protonation of carbanions using propan-2-ol.

[0126] Vicat softening temperatures are measured according to DIN EN ISO 306 - 2014-03. Unless stated otherwise, the A / 120 measurements were carried out.

[0127] Comparative Example 1

[0128] In a 50 L reactor, a block copolymer having the structure S-(S / B)-S, having styrene outer blocks each constituting 16 wt.-% of the polymer and a random-copolymerized styrenebutadiene block with 33 wt.-% styrene and 35% butadiene (based on the weight of the polymer) was synthesized by linear unidirectional polymerization followed by addition of terminating agent (propan-2-ol) as follows.

[0129] A) 15,07 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0130] B) 23.23 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 3.38 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0131] C) 720 g of dry styrene were added to the reactor, and the reaction continued until the monomer was consumed entirely, indicated by a peak in the temperature profile of the reaction mixture. D) A mixture of 1485 g dry styrene and 1575 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0132] E) 720 g of dry styrene were added to the reactor, and the reaction continued until the monomer was consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0133] F) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0134] G) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (6.08 g Irganox® 1010, BASF;

[0135] 8.1 g Irgafos® 168, BASF; and 6.08 g Sumilizer® GS, Sumimoto), extrusion using a twins-screw extruder at 180 °C, and pelletization.

[0136] Example 1

[0137] Using the same setup as in Comparative Example 1 , following polymerization was carried out, to prepare a polymer product having a similar chemical composition of the polymer blocks in the coupled polymer chains, as in Comparative Example 1 :

[0138] A1) 14,25 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0139] B1) 43.07 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 5.64 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0140] C1) 1520 g of dry styrene were added to the reactor, and the reaction continued until the monomer was consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0141] D1) A mixture of 1567.5 g dry styrene and 1662.5 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture. E1) 5 mL of ethyl acetate were added to the reactor as coupling agent and it was waited for 15 min.

[0142] F1) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0143] G1) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (6.41 g Irganox® 1010, BASF; 8.55 g Irgafos® 168, BASF; and 6.41 g Sumilizer® GS, Sumimoto), extrusion using a twins-screw extruder at 180 °C, and pelletization.

[0144] Example 2

[0145] Using the same setup as in Comparative Example 1 , following polymerization was carried out, to prepare a polymer product having a similar chemical composition of the polymer blocks in the coupled polymer chains, as in Comparative Example 1 :

[0146] A2) 13.5 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0147] B1) 35.82 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 4.64 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0148] C1) 1440 g of dry styrene were added to the reactor, and the reaction continued until the monomer was consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0149] D1) A mixture of 1485 g dry styrene and 1575 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0150] E1) 3 mL of ethyl acetate were added to the reactor as coupling agent and it was waited for 15 min.

[0151] F1) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0152] G1) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (6.41 g Irganox® 1010, BASF; 8.55 g Irgafos® 168, BASF; and 6.41 g Sumilizer® GS, Sumimoto), extrusion using a twins-screw extruder at 180 °C, and pelletization.

[0153] The properties of the polymer products obtained from Comparative Example 1 and Examples 1 and 2 and relevant synthesis parameters are shown in Table 1.

[0154] Table 1

[0155] In the block structures, S represents a styrene block, (S / B) represents a random copolymer block of styrene and butadiene, and (S / B)o.s represents the latter copolymer block having half length. In Examples 1 and 2, the (S / B) block in S-(S / B)-S is interrupted by a coupling centre derived from ethyl acetate (typically 1 -hydroxy-1 ,1 -ethylene).

[0156] It can be seen from Table 1 that the Examples according to the invention show a significant decrease in Shore hardness compared with Comparative Example 1 , while maintaining a similar or higher Vicat softening point and melt volume rate.

[0157] Comparative Example 2 In a 50 L reactor, a block copolymer having the structure (S / B)-(S / B)-(S / B) with different monomer compositions in the central and outer blocks was synthesized by linear unidirectional polymerization followed by addition of terminating agent (propan-2-ol) as follows. To allow quantitative initiation, 1 wt.-% of the styrene from the first block is dosed prior to dosing the rest of the block. The outer (S / B) blocks each contained 24 wt.-% styrene and 8 wt.-% butadiene (based on the total weight of the polymer), and the inner (S / B) block contained 17 wt.-% styrene and 19 wt.-% butadiene (based on the total weight of the polymer).

[0158] A3) 13,17 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0159] B3) 15.78 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 2.06 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0160] C3) 35 g of styrene were added to the reactor and the reaction continued for 5 min.

[0161] D3) A mixture of 805 g dry styrene and 280 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0162] E3) A mixture of 595 g dry styrene and 665 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0163] F3) A mixture of 840 g dry styrene and 280 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0164] G3) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0165] H3) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (4.73 g Irganox® 1010, BASF; 6.3 g Irgafos® 168, BASF; and 4.73 g Sumilizer® GS, Sumimoto), extrusion using a twins-screw extruder at 180 °C, and pelletization.

[0166] Example 3 Using the same setup as in Comparative Example 2, following polymerization was carried out to prepare a polymer product having a similar chemical composition of the polymer blocks in the coupled polymer chains, as in Comparative Example 2:

[0167] A4) 13,39 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0168] B4) 28.63 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 3.86 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0169] C4) 40 g of styrene were added to the reactor and the reaction continued for 5 min.

[0170] D4) A mixture of 1880 g dry styrene and 640 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0171] E4) A mixture of 680 g dry styrene and 760 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0172] F4) 5 mL of ethyl acetate were added to the reactor as coupling agent and it was waited for 15 min.

[0173] G4) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0174] H4) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (5.4 g Irganox® 1010, BASF;

[0175] 7.2 g Irgafos® 168, BASF; and 5.4 g Sumilizer® GS, Sumimoto), extrusion using a twins- screw extruder at 180 °C, and pelletization.

[0176] Example 4

[0177] Using the same setup as in Comparative Example 2, following polymerization was carried out, to prepare a polymer product having a similar chemical composition of the polymer blocks in the coupled polymer chains, as in Comparative Example 2: A4) 13,39 kg of cyclohexane as a solvent were introduced into the reactor and heated to 50 °C. 2 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane were added to the reactor, in order to dry the solvent.

[0178] B4) 30.34 g of a 13.8 wt.-% solution of sec-butyllithium in cyclohexane as the anionic polymerization initiator, and 4.05 g of a 5 wt.-% solution of potassium tert-amylate in cyclohexane as a randomizing agent were added to the reactor.

[0179] C4) 40 g of styrene were added to the reactor and the reaction continued for 5 min.

[0180] D4) A mixture of 1880 g dry styrene and 640 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0181] E4) A mixture of 680 g dry styrene and 760 g dry butadiene were added to the reactor, and the reaction continued until the monomers were consumed entirely, indicated by a peak in the temperature profile of the reaction mixture.

[0182] F4) 5 mL of ethyl acetate were added to the reactor as coupling agent and it was waited for 15 min.

[0183] G4) 25 mL of propan-2-ol as terminating agent were added to the reactor.

[0184] H4) The reaction mixture was further processed by addition of 10 g water and 8,3 g CO2 in order to reduce basicity and reactivity of any anionic components present in the reaction mixture, addition of stabilizers and other additives (5.4 g Irganox® 1010, BASF;

[0185] 7.2 g Irgafos® 168, BASF; and 5.4 g Sumilizer® GS, Sumimoto), extrusion using a twins- screw extruder at 180 °C, and pelletization.

[0186] The properties of the polymer products obtained from Comparative Example 2 and Examples 3 and 4 and relevant synthesis parameters are shown in Table 2.

[0187] Table 2

[0188] In the block structures, (S / B)arepresents outer random copolymer blocks of styrene and butadiene, (S / B)brepresents the central copolymer block of styrene and butdiene, and (S / B)bo.5 represents the latter copolymer block having half length.

[0189] In Examples 3 and 4, the (S / B)bblock in (S / B)a-(S / B)b-(S / B)ais interrupted by a coupling centre derived from ethyl acetate (typically 1 -hydroxy- 1,1 -ethylene).

[0190] It can be seen from Table 2 that the Examples according to the invention show a signif- icant decrease in Shore hardness compared with Comparative Example 1 , while maintaining a similar Vicat softening point and melt volume rate.

Claims

Patent claims1 . A method for the preparation of a polymer product (P1) by living anionic polymerization comprising the steps: i) performing anionic polymerization of at least one monomer (A) using at least one anionic polymerization initiator (I), which comprises an initiator complex of at least one nucleophilic carbanion (R-) and at least one metal cation (M+), to obtain a reaction mixture comprising at least one polymeric complex of at least one nucleophilic polymeric carbanion (P-) and at least one metal cation (M+), with repeating units of the at least one monomer (A) incorporated therein; and ii) terminating the anionic polymerization by combining the reaction mixture, comprising at least one polymeric complex of at least one nucleophilic polymeric carbanion (P-) and at least one metal cation (M+), with at least one coupling agent (C) and optionally at least one terminating agent (T), to obtain a polymer product (P1), wherein the at least one coupling agent (C) has a functionality fcof at least 2, preferably 2 to 4, more preferably 2 to 3, more preferably 2, where the functionality fcdefines the maximum number of nucleophilic polymeric carbanion (P-) molecules that can be coupled together by the coupling agent (C) to form coupled polymer chains (P-P), and wherein the following condition applies: fc■ n(C) + n(T) > n(P’), where n(P") is the molar amount of nucleophilic polymeric carbanions (P-) used in step ii), n(C) is the molar amount of the at least one coupling agent (C) used in step ii), and n(T) is the molar amount of the optional at least one terminating agent (T) used in step ii), wherein the at least one coupling agent (C) and the amount thereof and optionally the at least one terminating agent (T) and the amount thereof, which are combined with the at least one nucleophilic polymeric carbanion (P-) in step ii), are selected, thus that a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) to form coupled polymer chains (P-P) and a portion of the at least one nucleophilic polymeric carbanion (P-) reacts with the at least one coupling agent (C) and / or the at least one terminating agent (T) to form terminated polymer chains (P), where the terminated polymer chains (P) comprise polymer chains (Pc) that were terminated by the at least one coupling agent (C) and / or polymer chains (PT) that were terminated by the at least one terminating agent (T),and where the polymer product (P1) obtained in step ii) comprises a mixture of terminated polymer chains (P) and coupled polymer chains (P-P).

2. The method according to claim 1 , wherein the at least one monomer (A) is selected from the group of aromatic vinyl monomers, conjugated diene monomers, and mixtures thereof, preferably styrene, butadiene and mixtures thereof, more preferably styrene and mixtures thereof with butadiene.

3. The method according to claim 1 or 2, wherein the terminating agent (T) is combined with the at least one nucleophilic polymeric carbanion (P-) after the reaction of the at least one nucleophilic polymeric carbanion (P-) with the coupling agent (C) to form coupled polymer chains (P-P) is at least partially, preferably fully, completed.

4. The method according to any one of claims 1 to 3, wherein the ratio n(P-) fc ■ (c) in step ii) is in the range from 0.1 to 1.5, preferably from 0.2 to 1.2, more preferably from 0.3 to 1 .1 , more preferably from 0.5 to 1 .0.

5. The method according to any one of claims 1 to 4, wherein the coupling agent (C) comprisesA) at least one, preferably one group (F1) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a reaction cascade comprising a nucleophilic addition reaction, an elimination of a leaving group and a further nucleophilic addition reaction;B) at least two, preferably two groups (F2) capable of reacting with the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic addition or substitution reaction thereby each forming an anionic moiety within the formed terminated polymer chain (Pc), wherein the at least two groups (F2) are preferably located at a distance to each other of not more than 10, preferably not more than 6, more preferably not more than 3 covalent bonds;C) at least two, preferably two groups (F3) capable of being substituted by the at least one nucleophilic polymeric carbanion (P-) in a nucleophilic substitution reaction, preferably SN1 reaction, wherein the at least two groups (F3) are preferably located at a distance to each other of not more than 4, preferably not more than 2 covalent bonds;D) a combination of at least two groups selected from (F1), (F2) and (F3), wherein the at least two groups are preferably located at a distance to each other of not more than 10, preferably not more than 6, more preferably not more than 3 covalent bonds.

6. The method according to any one of claims 1 to 5, wherein the coupling agent (C) comprises functional groups selected from ester groups, halogenated hydrocarbon groups, epoxide groups, acrylate groups and methacrylate groups, preferably wherein the coupling agent (C) is a carboxylic acid ester, more preferably a carboxylic acid alkyl ester, more preferably an alkyl acetate, more preferably ethyl acetate.

7. The method according to any one of claims 1 to 6, wherein the at least one monomer (A) is added in step i) in a sequence leading to a homopolymer of at least one aromatic vinyl repeating unit, or a block copolymer comprising at least one block of aromatic vinyl repeating unit and at least one block comprising at least one conjugated diene repeating unit or a mixture thereof with at least one aromatic vinyl repeating unit.

8. The method according to any one of claims 1 to 7, wherein the method is for the preparation of a polymer product (P1) with lower Shore hardness, higher Vicat softening temperature or a combination thereof compared with a reference polymer product (P2) having a target melt volume rate, and the method comprises following steps:I) selecting a reference polymer product (P2) having a target melt volume rate MVRP2, and further having a peak molecular weight MP)P2, a Vicat softening temperature VSTP2and a Shore hardness SHP2, wherein the polymer product (P2) is obtained by linear unidirectional anionic polymerization terminated in the absence of a coupling agent, and has a linear, essentially symmetrical structure;II) carrying out the method according to any one of claims 1 to 7, wherein following conditions apply: a) in step i), the anionic polymerization of the at least one monomer (A) is carried out in a monomer sequence corresponding to the monomer sequence of the polymer product (P2) from one terminal end of polymer product (P2) to the centre of polymer product (P2); b) in step i), the anionic polymerization of the at least one monomer (A) is carried out up to a peak molecular weight Mp P, which satisfies the condition 0.4 ■ Mpp2— Mpp < 0.8 ■ Mp,p2, c) in step ii), a coupling agent (C) having a functionality fcof 2 is used, and a polymer product (P1) with a peak molecular weight Mp P1is obtained, which satisfies the condition 1.8 ■ Mp P< Mp P1< 2.2 ■ MPtPto obtain a polymer product (P1) having a melt volume rate MVRP1, a Vicat softening temperature VSTP1and a Shore hardness SHP1, wherein the melt volume rate MVRP1of the obtained polymer product (P1) deviates by not more than 40% from the target melt volume rate MVRP2, and wherein, VSTP1> VSTP2, and / or SHP1< SHP2.

9. The method according to any one of claims 1 to 8, wherein in step ii) the coupling agent (C) is combined with the at least one nucleophilic polymeric carbanion (P-) having a weight average molecular weight Mw Pto obtain a polymer product (P1) having a weight average molecular weight Mw P1and where 1.20 ■ Mw P< Mw P1< 1.99 ■ Mw P, preferably 1.49 ■ Mw P< Mw P1< 1.98 ■ Mw P, more preferably 1.75 ■ Mw P< Mw P1< 1.95 ■ Mw P, more preferably 1.90 ■ Mw P< Mw P1< 1.93 ■ Mw P10. A polymer product (P1) obtained by the method according to any one of claims 1 to 9.11 . The polymer product (P1) according to claim 10, wherein the polymer product (P1) comprises from 1 to 60 wt-%, preferably from 5 to 50 wt-%, more preferably from 10 to 40 wt-%, more preferably from 15 to 30 wt-%, based on the total weight of terminated polymer chains (P) and coupled polymer chains (P-P), of terminated polymer chains (P) and from 40 to 99 wt-% by weight, more preferably from 70 to 90 wt-%, based on the total weight of terminated polymer chains (P) and coupled polymer chains (P-P), of coupled polymer chains (P-P).

12. The polymer product (P1) according to claim 10 or 11 , having a Shore (D) hardness, measured according to ISO 868 using a durometer, in the range of from 20 to 40, preferably from 25 to 35, more preferably from 27 to 33, a Vicat softening temperature (A / 120), measured according to ISO 306 in the range of from 30 to 60 °C, preferably from 35 to 50 °C, more preferably from 36 to 42 °C, a melt volume rate measured at 200 °C under a load of 5 kg according to DIN ISO 1133-1 :2012-03 in the range of from 10 to 20 cm3 / 10 min, preferably from 11 to 17 cm3 / 10 min, more preferably 13 to 15 cm3 / 10 min, and a peak molecular weight Mp P1, measured by gel permeation chromatography calibrated to polystyrene standards, in the range of from 100 to 200 kg / mol, preferably 135 to 180 kg / mol, more preferably from 140 to 150 kg / mol.

13. The polymer product (P1) according to any one of claims 10 to 12, wherein the terminated polymer chains (P) comprise, preferably consist of, a sequence of a first polymer block and a second polymer block, wherein the repeating units in the first polymer block are aromatic vinyl repeating units, preferably styrene repeating units, and the repeating units in the second polymer block are conjugated diene repeating units, preferably butadiene repeating units, or a random or tapered mixture thereof with aromatic vinyl repeating units, preferably styrene repeating units, and wherein the coupled polymer chains (P-P) comprise, preferably consist of, two said sequences coupled together by the coupling agent (C) via said second polymer block.

14. The polymer product (P1) according to any one of claims 10 to 13, wherein the terminated polymer chains (P) have a block copolymer structure S-(S / B)r, and the coupled polymer chains (P-P) have a block copolymer structure S-(S / B)r-X-(S / B)r-S, wherein S represents a block of styrene repeating units, wherein all blocks S have essentially the same length, (S / B)rrepresents a block of randomly or tapered copolymerized styrene and butadiene repeating units, wherein all blocks (S / B)rhave essentially the same length and X represents the coupling centre formed from the coupling agent (C), preferably a carboxylic acid alkyl ester, more preferably an alkyl acetate, more preferably ethyl acetate, and wherein the amount of butadiene repeating units in the polymer product (P1) is in the range of from 20 to 50% by weight, preferably 25 to 45% by weight, more preferably 30 to 40% by weight, based on the total weight of repeating units in the polymer product (P1), and the amount of blocks represented by (S / B)ris in the range of from 50 to 80% by weight, more preferably from 55 to 75% by weight, more preferably from 60 to 72% by weight, more preferably from 65 to 70% by weight, based on the total weight of the polymer product (P1).

15. The polymer product (P1) according to any one of claims 10 to 14, comprising polymer chains represented by following structure (P-PA) and polymer chains represented by one or more of following structures (PCA), (PCB) and / or (PTA):where R1is the organic residue of the initiator (I), preferably C1-C4 alkyl, more preferably n-butyl, iso-butyl, sec-butyl or tert-butyl; R2is the organic residue of the carboxylic acid part of a carboxylic acid ester, preferably C1-C4 alkyl, more preferably methyl; R3is the organic residue of the alcohol part of a carboxylic acid ester, preferably C1-C4 alkyl, more preferably ethyl; b indicates a transition between two polymer blocks and r indicates a random or tapered distribution of repeating units within a polymer block.

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