Rubber-toughened vinyl aromatic (co)polymers and their preparation process.

Abstract

A rubber-reinforced vinyl aromatic (co)polymer comprising: (a) a polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer; and (b) dispersed therein rubber particles obtained by a continuous bulk process from a functionalized low-cis polybutadiene rubber (LCBR), characterized in that: (i) the average volume diameter of the rubber particles is between 0.25 μm and 0.37 μm, preferably between 0.26 μm and 0.36 μm, more preferably between 0.27 μm and 0.35 μm; (ii) the volume of the rubber particles having a diameter larger than 0.40 μm is between 20% and 50%, preferably between 25% and 45%, more preferably between 30% and 40%, based on the total volume of the dispersed rubber particles; and (iii) the ratio of rubber particles containing occlusions to rubber particles not containing occlusions (particles containing occlusions / particles not containing occlusions) is between 0.9 and 1.9, preferably between 1.0 and 1.8, more preferably between 1.2 and 1.7. The rubber-reinforced vinyl aromatic (co)polymers described above have high aesthetic properties, especially in terms of gloss and gloss sensitivity, and high mechanical properties, especially in terms of impact resistance and puncture resistance. The rubber-reinforced vinyl aromatic (co)polymers described above can be advantageously used in various applications, such as injection molding.

Description

[Technical field]

[0001] The present invention relates to rubber-toughened vinyl aromatic (co)polymers. [Background technology]

[0002] More particularly, the present invention relates to a rubber-reinforced vinyl aromatic (co)polymer comprising: (a) a polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer; and dispersed therein, rubber particles obtained in a continuous bulk process from a functionalized low-cis polybutadiene rubber (LCBR) and having specific characteristics in terms of size and morphology.

[0003] The aforementioned rubber-reinforced vinyl aromatic (co)polymers have high aesthetic properties, especially in terms of gloss and gloss sensitivity, and high mechanical properties, especially in terms of impact resistance and puncture resistance.

[0004] The aforementioned rubber-toughened vinyl aromatic (co)polymers can be advantageously used in a variety of applications, such as injection molding.

[0005] A further object of the present invention is also a process for the preparation of said rubber-toughened vinyl aromatic (co)polymers.

[0006] The balance of aesthetic and mechanical properties of rubber-toughened vinyl aromatic (co)polymers is known to depend on the rubber concentration in the finished (co)polymer and the mean volume diameter distribution of the rubber particles dispersed in the polymer matrix.

[0007] For example, to obtain a rubber-reinforced vinyl aromatic (co)polymer, such as an acrylonitrile-butadiene-styrene (ABS) copolymer, with good mechanical properties and high surface gloss, it is necessary that the concentration of rubber in the copolymer is higher than 13% by mass, that the rubber particles have an average volume diameter of less than 0.5 μm and a wide volume diameter distribution of 0.1 μm to 0.5 μm, preferably bimodal. If any of these parameters are not met, the desired mechanical properties and surface gloss are not obtained and the resulting (co)polymer is therefore not suitable for the end use. For example, a rubber-reinforced vinyl aromatic (co)polymer with a rubber particle content of 15% by mass, with an average particle volume diameter of 0.2 μm and a narrow volume diameter distribution of 0.1 μm to 0.3 μm, has a high surface gloss but does not have good mechanical properties.

[0008] The morphology of the rubber particles dispersed in the polymer matrix is ​​also very important in defining the aesthetic and mechanical properties of rubber-toughened vinyl aromatic (co)polymers. To precisely control these properties, it is necessary that the elastomeric phase (i.e. rubber particles) dispersed in the polymer matrix contains particles with small to medium volume diameters (generally less than 0.3 μm) and spherical or capsule morphology (with single occlusions) and particles with larger average volume diameters (0.3 μm to 0.5 μm) with "salami" (i.e. multiple occlusions) morphology.

[0009] For example, EP 0 390 781 and US 4 713 420 relate to rubber modified acrylonitrile-butadiene-styrene (ABS) copolymers containing three different types of rubber particles. In particular, the rubber particles are: 1) rubber particles produced by emulsion process, having a small average volume diameter of 0.05 μm to 0.25 μm; 2) rubber particles produced by emulsion process, having a large average volume diameter of 0.4 μm to 2 μm; e3) rubber particles produced by bulk process, having a large average volume diameter of 0.5 μm to 10 μm. In particular, the patents show how rubber particles with an average volume diameter larger than 0.5 μm promote the mechanical properties of the copolymer while impairing its aesthetic properties, especially gloss. Therefore, to ensure a proper balance between mechanical and aesthetic properties, the rubber modified acrylonitrile-butadiene-styrene (ABS) copolymers are obtained in the said patent by precisely blending different components, in particular different rubber particles based on their average volume diameter and their morphology. The rubber modified acrylonitrile-butadiene-styrene (ABS) copolymers in the said patent are said to have a good balance between aesthetic and mechanical properties.

[0010] US Patent No. 6,211,298 relates to an improved rubber modified polymer composition comprising: (a) a continuous phase matrix comprising an interpolymer of monovinylidene aromatic monomers and ethylenically unsaturated nitrile monomers; and (b) discrete rubber particles dispersed in said matrix, said rubber particles being 5% to 40% by weight based on the total weight of said polymer composition, said dispersed rubber particles comprising: (1) at least 33% by weight based on the total rubber content of rubber particles produced by a bulk process having an average volume diameter of 0.15 μm to 0.40 μm; (2) 15% to 67% by weight based on the total rubber content of rubber particles produced by an emulsion process having a small average volume diameter of 0.05 μm to 0.30 μm; and (3) 0% to 35% by weight based on the total rubber content of rubber particles produced by an emulsion process having a large average volume diameter of greater than 0.30 μm up to 2.0 μm; said rubber particles having an average absorptivity of less than 1.4. The compositions, which contain a high percentage of rubber particles produced in agglomerates having small to medium volume diameters, are said to be less expensive and to be able to maintain excellent gloss and good impact properties.The compositions are also said to have improved thermal and color stability compared to similar compositions having similar gloss and gloss sensitivity.

[0011] As is known in the art, rubber particles can be produced by two types of processes: emulsion polymerization process and continuous bulk polymerization process.

[0012] In emulsion polymerization processes, it is known to arbitrarily adjust the size of rubber particles at an early stage of the process by radical polymerization of butadiene in an aqueous emulsion. The rubber particles with defined dimensions are then subjected to grafting with styrene and acrylonitrile. The product of this reaction is called grafted acrylonitrile-butadiene-styrene (ABS) copolymer and is characterized by a high concentration of polybutadiene; the presence of styrene-acrylonitrile (SAN) copolymer chemically grafted to the polybutadiene particles is of fundamental importance for the compatibilization of polybutadiene in styrene-acrylonitrile (SAN) copolymers, since the two polymers are not compatible with each other. The emulsion manufacturing process of acrylonitrile-butadiene-styrene (ABS) copolymers includes a step of compounding the grafted acrylonitrile-butadiene-styrene (ABS) copolymer with a separately manufactured styrene-acrylonitrile (SAN) copolymer to obtain the desired product. Details of the emulsion polymerization process are described, for example, in Bouquet G., “Rubber Particle Formation in Mass ABS, Modern Styrenic Polymers: Polystyrenes and Styrenic Copolymers” (2003), Chapter 14, pg. 305-319, Edited by J. Scheirs and DB Priddy, Wiley & Sons.

[0013] On the other hand, in the continuous bulk polymerization process, the formation of rubber particles dispersed in a matrix starts with a solution of polybutadiene in a mixture of monomer (styrene) and diluent (usually ethylbenzene), to which a second monomer (acrylonitrile) is added just before the continuous bulk polymerization reaction. This precaution is necessary because at the temperatures at which the dissolution of the rubber takes place, the presence of acrylonitrile will cause the rubber to precipitate. Once the reaction mixture is prepared, it is subjected to a radical polymerization process; as the radical polymerization reaction proceeds, styrene-acrylonitrile (SAN) copolymer domains are formed in the polybutadiene-monomer-diluent mixture, of which the predominant polymer phase is the polybutadiene phase. After a certain degree of monomer conversion, the volumes of the polybutadiene phase and the styrene-acrylonitrile (SAN) copolymer phase in the reaction system become equal: this moment is called phase inversion. As the monomer conversion proceeds in the formation of styrene-acrylonitrile (SAN) copolymer, the main phase in the reaction mixture is composed of styrene-acrylonitrile (SAN) copolymer and the dispersed phase is composed of polybutadiene particles dispersed in the main phase of styrene-acrylonitrile (SAN) copolymer. Immediately after the phase inversion phenomenon, the diameter and morphology of the dispersed rubber particles are defined.

[0014] It is also known that the main parameters that influence the diameter and morphology of rubber particles are: -shear stress (or "shear") on the reaction mixture; - the interfacial tension between the two polymer phases [polybutadiene and styrene-acrylonitrile (SAN) copolymer] present in the reaction mixture; - Viscosity ratio of polybutadiene phase to styrene-acrylonitrile (SAN) copolymer phase.

[0015] Furthermore, to obtain acrylonitrile-butadiene-styrene (ABS) copolymers containing rubber particles having an average volume diameter of less than 0.5 μm, and to maximize the gloss and mechanical properties of the final product, a continuous bulk polymerization process requires: -Maximize the shear stress on the reaction mixture by mechanical agitation; -Proper control of the formation of graft copolymers to precisely control the interfacial tension; - Minimizing the viscosity ratio of the polybutadiene phase to the styrene-acrylonitrile (SAN) copolymer phase, thus minimizing the need to use low viscosity rubbers and maximizing the viscosity of the styrene-acrylonitrile (SAN) copolymer formed during the reaction.

[0016] This literature describes various technical solutions for the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers by a continuous bulk polymerization process using rubber particles with an average volume diameter of less than 0.5 μm, allowing for maximization of the grafting reaction in combination with the use of low viscosity rubbers.

[0017] In fact, it is known that the use of a bifunctional radical polymerization initiator at a temperature below 115°C in the initial stage of the polymerization reaction increases the amount of styrene-acrylonitrile (SAN) copolymer grafted onto polybutadiene, resulting in a high molecular weight of the styrene-acrylonitrile (SAN) copolymer phase. However, the low weight average molecular weight (M w ) polybutadiene concentration is greater than 9%, and the weight average molecular weight (M w ) is high, the condition of partial crosslinking of the elastomeric phase (i.e., rubber particles) is met because the polymer chains of styrene-acrylonitrile (SAN) copolymer can be grafted to two polymer chains of polybutadiene of two different rubber particles.

[0018] For example, US Pat. No. 5,414,045 relates to a composition obtained by a continuous bulk polymerization process by reaction of a continuous phase comprising a vinyl aromatic monomer, an unsaturated nitrile monomer and a diene-based polymerized rubber dissolved in said monomer, said composition comprising a graft copolymer and a free rubber copolymer, said graft copolymer comprising a diene-based rubber substrate and a vinyl aromatic / unsaturated nitrile copolymer grafted to said substrate, said rubber substrate having an average particle size of less than 0.3 μm, said rubber substrate having both an inner and outer surface and a cell morphology defined as a network of rubber membranes having spherical surfaces containing occlusions of vinyl aromatic / unsaturated nitrile copolymer within the rubber substrate, said vinyl aromatic / unsaturated nitrile copolymer being grafted to both the inner and outer surfaces of the rubber substrate, said composition having a gloss measured by a "grader gloss meter" at 60° of greater than 90%. The polymerization reaction is carried out in a plug flow reactor (PFR) and the reaction mixture leaving said reactor is fed to a continuous stirred tank reactor (CSTR) having a vinyl aromatic / unsaturated nitrile copolymer content in excess of that required to complete phase inversion.

[0019] US Patent No. 7,132,474 relates to a continuous bulk process for preparing acrylonitrile-butadiene-styrene (ABS) copolymers, which comprises the steps of: a) preparing a solution containing styrene monomer and acrylonitrile monomer by adding 5%-10% by weight of a mixture of styrene monomer and acrylic monomer in a reaction solvent; b) preparing a polymerization solution by dissolving butadiene rubber in said solution containing styrene monomer and acrylonitrile monomer; c) polymerizing the solution prepared in step b) and an initiator by continuous injection in a grafting reactor; polymerizing the reaction mixture obtained in step c) by adding 90%-95% by weight based on the total weight of the reaction mixture of styrene monomer and acrylic monomer in a phase inversion reactor; e) further polymerizing the reaction mixture obtained in step d) at 130°C-160°C. The aforementioned composition is said to have excellent impact resistance and excellent gloss.

[0020] However, the aforementioned process is complex and involves the use of continuous tank reactors (CSTRs), which are generally not recommended for the production of acrylonitrile-butadiene-styrene (ABS) copolymers.

[0021] Another way to increase the concentration of grafted polymers in the production of rubber-toughened styrene (co)polymers, such as high impact polystyrene (HIPS), by continuous bulk processing is to use diblock rubbers.

[0022] In the production of high impact polystyrene (HIPS), in order to obtain rubber particles of elastomeric phase in capsule form (single occlusion) with an average volume diameter of less than 0.5 μm and high gloss, it is in fact known to supply a styrene-polybutadiene block polymer containing 60% by weight of polybutadiene with respect to the total weight of the polymer. Unfortunately, in the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers, the use of polybutadiene-styrene-acrylonitrile block copolymers (polybutadiene-SAN) is not possible, since acrylonitrile does not polymerize anionically.

[0023] However, known techniques report processes to accentuate and promote "in situ" the formation of graft copolymers polybutadiene-styrene-acrylonitrile (polybutadiene-SAN) during the polymerization process of a mixture of polybutadiene, styrene and acrylonitrile. To accentuate the reaction of polybutadiene with the mixed monomers of styrene and acrylonitrile, rubbers are used that contain active radical sites in their molecular structure that can be activated at the temperatures used in the radical polymerization process.

[0024] For example, EP 1592722 relates to a bulk / solution process using functionalized rubber to produce vinyl aromatic monomer modified polymer rubber, comprising polymerizing vinyl aromatic monomer by a linear process using one or more polymerization reactors in the presence of rubber, said rubber comprising: a) a functionalized styrene-butadiene block copolymer having a solution viscosity (5% in styrene at 20°C) of 5 cps to less than 50 cps; b) a radical polymerization controllable such that grafted rubber particles are formed and dispersed in a matrix containing polymerized vinyl aromatic monomer and have a broad unimodal size distribution, said rubber being present in an amount of 5% to 25% by weight based on the total weight of the polymerization mixture. The modified polymer rubber thus obtained is said to have high gloss and high hardness.

[0025] US Patent No. 7,115,684 relates to a rubber modified polymer composition obtained by continuous bulk polymerization, said rubber modified polymer composition comprising: a matrix consisting of a continuous phase comprising a polymer of monovinylidene aromatic monomers and optionally ethylenically unsaturated nitrile monomers; and discrete rubber particles dispersed in said matrix, said rubber particles being made from a rubber component comprising 5% to 10% by weight of a functionalized diene rubber having at least one functional group per rubber polymer chain capable of controlling radical polymerization; wherein said composition is further characterized by: a) an average volume diameter of about 0.15 μm to 0.35 μm; a total volume of rubber phase of 12% to 45% by weight based on the total weight of matrix and rubber particles; c) a partial volume of rubber phase of 2% to 20% characterized by rubber particles having an average volume diameter of more than 0.40 μm; and d) a crosslinked rubber fraction of at least 85% by weight based on the total weight of rubber particles. The aforementioned composition is said to have high gloss and high gloss sensitivity while maintaining good hardness properties.

[0026] In the above-mentioned EP 1592722 and US 7115684, functionalized rubbers having at least one functional group per rubber polymer chain capable of promoting the formation of graft copolymers are obtained by anionic polymerization of polybutadiene and styrene. The anionic reaction is terminated with a compound containing a nitroxyl functionality (i.e. an organic compound containing a nitrogen-oxygen bond) so that the styrene-butadiene rubber (SBR) contains said group as a polymer chain end. When said rubber is used in a continuous bulk polymerization process for the production of acrylonitrile-butadiene-styrene (ABS) copolymers, the nitroxyl functionality dissociates to generate terminal radical sites on the styrene-butadiene rubber chains (SBR) which can react with styrene and acrylonitrile monomers to form grafted polybutadiene-styrene-acrylonitrile copolymers (polybutadiene-SAN) in situ. Descriptions of the synthesis process of rubbers terminated with polymer chain ends containing nitroxyl groups are found, for example, in U.S. Pat. No. 5,721,320, cited in EP 1,592,722, and in U.S. Pat. No. 7,115,684, reported above.

[0027] However, the industrial application of EP 1592722 and the above reported US Pat. No. 7115684 is limited by the unavailability of functionalized rubber commercially. Moreover, functionalized styrene-butadiene block copolymers are used in said patents in order to minimize the viscosity ratio between the polybutadiene phase and the styrene-acrylonitrile (SAN) matrix (which is another fundamental parameter for obtaining rubber particles with an average volume diameter of less than 0.5 μm). This necessity stems precisely from the process used in said patents, which in fact prescribes the preparation of a solution of rubber in the mixture of monomers to be subjected to the polymerization process. Industrially, in order to prepare this mixture, it is necessary to subject the polybutadiene to a step of dissolving in the mixture of monomers: it is therefore necessary to produce the polybutadiene, then to subject it to a finishing step (a step of removing the solvent in which it was synthesized) and then to grinding in order to subject it to a dissolving step. As described in the aforementioned patents, if the viscosity of the rubber is particularly low, the finishing step followed by the grinding step is technically difficult, if not impossible. It is therefore necessary to structurally modify the rubber by inserting blocks of polystyrene into the polymer chain in order to increase the viscosity of the rubber itself and to make the finishing stage and subsequent grinding possible.

[0028] However, as described in the above-mentioned US Patent No. 5,721,320, the use of styrene-butadiene rubber (SBR) in the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers is economically disadvantageous for two reasons: the inherent cost of styrene-butadiene rubber (SBR) and the manufacturing process of acrylonitrile-butadiene-styrene (ABS) copolymers forces the supply of more styrene-butadiene rubber (SBR) compared to polybutadiene rubber. In fact, the properties of acrylonitrile-butadiene-styrene (ABS) copolymers depend on the polybutadiene concentration in the final product: since the polybutadiene content in styrene-butadiene block rubber (SBR) is less than 100%, it is necessary to supply more styrene-butadiene (SBR) rubber blocks to achieve the desired polybutadiene concentration in the acrylonitrile-butadiene-styrene (ABS) copolymer. Finally, if it is necessary to adjust the amount of graft copolymer formed "in situ" from the use of said rubber, it is necessary to take into account the fact that it is necessary to provide a mixture of functionalized styrene-butadiene rubber (SBR) and non-functionalized rubber. In fact, as reported in the aforementioned EP 1592722 and US 7115684, the functionalized rubber must contain at least one functional group per rubber polymer chain. In this way, if the amount of graft copolymer formed with the functionalized rubber is excessive, it is necessary to reduce the concentration of active sites in the reaction mixture by adding a non-functionalized rubber whose rubber chains contain on average less than one active site (as also described in the examples of the aforementioned patents). The use of two rubbers complicates the production process and increases the production costs.

[0029] Other processes are also known that are useful for obtaining polymers functionalized with nitroxyl groups capable of facilitating subsequent grafting reactions.

[0030] For example, US Pat. No. 6,525,151 relates to a process for preparing a graft polymer, in which in a first step A), a stable nitroxyl radical is grafted onto a polymer, which step comprises heating the polymer and the stable nitroxyl radical (NO●) at a temperature of 150° C. to 300° C. in a reactor suitable for mixing molten polymers; in a second step B), the graft polymer of step A) is heated in the presence of an ethylenically unsaturated monomer or oligomer to a temperature at which cleavage of the nitroxyl-polymer bond occurs and polymerization of the ethylenically unsaturated monomer or oligomer on the polymer radical begins; said temperature is maintained to continue the polymerization, and then cooled to a temperature below 60° C.

[0031] The functionalization process described in the aforementioned US Pat. No. 6,525,151 is very effective and allows the amount of nitroxyl bonds formed per single rubber polymer chain to be freely adjusted. Therefore, even if it is necessary to use polybutadiene polymer chains containing less than one active site per polymer chain, it is not necessary to use two rubbers (functionalized and non-functionalized). However, in the functionalization process described in the aforementioned patent, the functionalization reaction is carried out on the molten polymer: at an industrial level, this involves additional processing and therefore increased costs compared to the standard process.

[0032] US Pat. No. 6,335,401 relates to graft copolymers containing graft groups having the following general formula (I): [ka] During the ceremony, PM1 represents a polymer block resulting from the radical (co)polymerization of at least one monomer M1; PM2 is optionally present and represents a polymer block resulting from the (co)polymerization of at least one monomer M2 by a radical process; T is a stable radical T * represents a residue of

[0033] Said (co)polymers are synthesized starting from a polymer (e.g. polyethylene) reacted with ozone and then propagated with a monomer (e.g. styrene) in the presence of stable nitroxyl radicals, but even this process, although very effective, is difficult to apply industrially.

[0034] Further processes in solution are also known which are useful for obtaining functionalized polymers bearing nitroxyl groups capable of promoting subsequent grafting reactions.

[0035] For example, US Pat. No. 6,255,402 relates to a process for the synthesis of functionalized rubbers, in particular high impact polystyrene (HIPS), with groups capable of generating stable free radicals (e.g., nitroxyl groups), which comprises heat treating an elastomer in the presence of a stable free radical, a free radical initiator capable of abstracting a proton from the elastomer, and a solvent, in the absence of a vinyl aromatic monomer, so that the rubber is functionalized with, on average, 0.1 to 10 functional groups capable of generating stable free radicals per rubber polymer chain. The functionalized rubber thus obtained, e.g., polybutadiene functionalized with nitroxyl groups, is then subjected to radical polymerization in the presence of a vinyl aromatic monomer, e.g., styrene, so that a grafted polybutadiene-polystyrene copolymer is formed "in situ". The functionalization reaction is carried out by dissolving the polybutadiene in the presence of a radical initiator and a compound containing stable free nitroxyl radicals in a diluent (usually ethylbenzene) used for the subsequent synthesis of high impact polystyrene (HIPS). The reaction mixture thus prepared is heated to a temperature sufficient to favor the dissociation of the radical initiator. The solution of functionalized rubber in the diluent after addition of styrene and additives is subjected to a radical polymerization process to obtain the final high impact polystyrene (HIPS). The final properties of the high impact polystyrene (HIPS) can be varied in terms of balance between mechanical and aesthetic properties by changing the amount of radical initiator / stable free nitroxyl radical system in the functionalization reaction of the rubber in the diluent.

[0036] The functionalization of polybutadiene in solution is an effective technique and allows the amount of nitroxyl functional groups generated per single polymeric rubber chain to be freely adjusted by the reaction of the polybutadiene with stable free nitroxyl radicals. Therefore, it is not necessary to use two rubbers (functionalized and non-functionalized) when it is necessary to use polybutadiene containing less than one active site per rubber polymeric chain. However, this process also has drawbacks due to the maximum amount of polybutadiene that can be reached in the final polymer. In the examples reported in the aforementioned US Pat. No. 6,255,402, the rubber functionalization reaction is in fact carried out by preparing a solution of polybutadiene in 20% by weight of diluent. The subsequent addition of styrene results in a concentration of polybutadiene of 6% in the reaction and in the amount of diluent of 24% in the reaction. These amounts of reagents are compatible with the synthesis of high impact polystyrene (HIPS) but not with the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers. In fact, the minimum concentration of rubber in acrylonitrile-butadiene-styrene (ABS) copolymers to have a high mechanical strength / aesthetic balance must be at least 13%. Assuming the use of the same amount of diluent (24%), the polybutadiene concentration in the rubber dissolution / functionalization stage must be at least 40%. This rubber concentration cannot be technically managed in continuous bulk production plants due to the high viscosity of the rubber solution in the diluent. Moreover, a diluent concentration of 24% in the reaction reduces the plant's own production capacity and, as a result, increases production costs.

[0037] Processes for the preparation of rubber-reinforced styrene polymers in the presence of stable free nitroxyl radicals without functionalization reactions are also known, but in this case a wide distribution of the average volume diameter of the rubber particles is always obtained.

[0038] For example, US Patent No. 6,262,179 relates to a process for producing a composition comprising a matrix containing vinyl aromatic polymer or copolymer in which rubber particles are dispersed, said process comprising a polymerization step in the presence of at least one vinyl aromatic monomer and at least one rubber, during which phase inversion occurs and rubber particles are formed, said polymerization being thermally or by a polymerization initiator, stable free radicals (e.g. nitroxyl radicals) are present during the polymerization step in an amount of at least 10 ppm relative to the total amount of vinyl aromatic monomers (e.g. styrene), characterized by a broader size distribution of rubber particles compared to the absence of stable free radicals.In this way, a broad size distribution of rubber particles is obtained, said rubber particles having an average size that is always larger than the size required to guarantee the properties of acrylonitrile-butadiene-styrene (ABS) copolymer a (i.e. 0.5 μm or less).

[0039] US Patent No. 6,815,500 relates to a process for preparing a composition comprising a vinyl aromatic polymer matrix containing rubber particles, comprising the step of polymerizing at least one vinyl aromatic monomer in the presence of a rubber, a polymerization initiator and a stable free radical, said process being characterized by the following ratio of the formula:

number

[0040] The rubber functionalization reaction can also be carried out in solution with diluent and monomers in the presence of a radical initiator and a stable free nitroxyl radical in order to reduce the rubber concentration at this step of the process, as described, for example, in patent applications WO 2005 / 100425 and WO 2006 / 063719. However, even in this case, the maximum concentration of polybutadiene obtained in the final product is compatible with the synthesis of high impact polystyrene (HIPS), but not with the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers.

[0041] The rubber functionalization reaction can also be carried out directly downstream of the anionic polymerization of butadiene by promoting the termination reaction of the polybutadiene chains with bromoalkanes and stable free nitroxy radicals, as described, for example, in patent application WO 2010 / 020374. However, even in this case, the limit is set by the maximum concentration of polybutadiene obtained in the final product, which is not compatible with the synthesis of acrylonitrile-butadiene-styrene (ABS) copolymers.

[0042] Rubber-reinforced vinyl aromatic (co)polymers, especially acrylonitrile-butadiene-styrene (ABS) copolymers, with their high aesthetic and high mechanical properties, still attract great interest, so the research of new rubber-reinforced vinyl (co)polymers still attracts great interest.

[0043] The Applicant therefore set himself the problem of finding new rubber-reinforced vinyl aromatic (co)polymers, in particular acrylonitrile-butadiene-styrene (ABS) copolymers, which have high aesthetic properties, in particular in terms of gloss and gloss sensitivity, and high mechanical properties, in particular in terms of impact resistance and puncture resistance.

[0044] The applicant has discovered a rubber-reinforced vinyl aromatic (co)polymer comprising: (a) a polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer; and (b) dispersed therein, rubber particles obtained by a continuous bulk process from a functionalized low-cis polybutadiene rubber (LCBR), the rubber particles having specific properties in terms of size and morphology.

[0045] The aforementioned rubber-reinforced vinyl aromatic (co)polymers have high aesthetic properties, especially in terms of gloss and gloss sensitivity, and high mechanical properties, especially in terms of impact resistance and puncture resistance.

[0046] The aforementioned rubber-toughened vinyl aromatic (co)polymers can be advantageously used in a variety of applications, such as injection molding.

[0047] The subject of the present invention is therefore: (a) a polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer; (b) having dispersed therein rubber particles obtained by a continuous bulk process from a functionalized low-cis polybutadiene rubber (LCBR): (i) the average volume diameter of the rubber particles is 0.25 μm to 0.37 μm, preferably 0.26 μm to 0.36 μm, and more preferably 0.27 μm to 0.35 μm; (ii) the volume of said rubber particles having a diameter larger than 0.40 μm is between 20% and 50%, preferably between 25% and 45%, more preferably between 30% and 40%, based on the total volume of the dispersed rubber particles; (iii) A rubber-reinforced vinyl aromatic (co)polymer, characterized in that the ratio of rubber particles containing blockages to rubber particles not containing blockages (particles containing blockages / particles not containing blockages) is 0.9 to 1.9, preferably 1.0 to 1.8, and more preferably 1.2 to 1.7.

[0048] For purposes of this specification and the claims that follow, numerical range definitions shall always include the extremes unless expressly stated otherwise.

[0049] For purposes of this specification and the claims that follow, the term "comprising" also includes the terms "which essentially consists of" or "which consists of."

[0050] According to a preferred embodiment of the present invention, the vinyl aromatic monomer may be chosen, for example, from vinyl aromatic monomers having the following general formula (I): [ka] In the formula, R is a hydrogen atom or a methyl group, n is 0 or an integer of 1 to 5, and Y is a halogen atom such as chlorine or bromine, or an alkyl or alkoxy group having 1 to 4 carbon atoms.

[0051] According to a preferred embodiment of the present invention, the vinyl aromatic monomer having said general formula (I) may be selected, for example, from: styrene, α-methylstyrene, methylstyrene, ethylstyrene, butylstyrene, dimethylstyrene, mono-, di-, tri-, tetra- and penta-chlorostyrene, bromo-styrene, methoxy-styrene, acetoxy-styrene, or mixtures thereof. Styrene, α-methylstyrene is preferred.

[0052] For the purposes of the present invention, the vinyl aromatic monomers having general formula (I) can be used alone or in admixture with other copolymerizable monomers up to a maximum of 50% by weight.

[0053] According to a preferred embodiment of the present invention, the comonomer may be selected from, for example: (meth)acrylic acid; C1-C4 alkyl esters of (meth)acrylic acid, such as, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, butyl acrylate; amides and nitriles of (meth)acrylic acid, such as, for example, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile; imides, such as, for example, N-phenylmaleimide; divinylaromatic monomers, such as, for example, divinylbenzene; anhydrides, such as, for example, maleic anhydride; or mixtures thereof. Acrylonitrile and methyl methacrylate are preferred.

[0054] According to a preferred embodiment of the present invention, in the rubber-reinforced vinyl aromatic (co)polymer, the polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer has a weight average molecular weight (M) of 145000 g / mol or less, preferably 140000 g / mol or less, more preferably 90000 g / mol to 135000 g / mol. w ).

[0055] According to a preferred embodiment of the present invention, in said rubber-toughened vinyl aromatic (co)polymer, the functionalized low-cis polybutadiene rubber (LCBR) is present in an amount of 5% to 35% by weight, preferably 8% to 30% by weight, more preferably 10% to 25% by weight, based on the total weight of the rubber-toughened vinyl aromatic (co)polymer.

[0056] According to a preferred embodiment of the present invention, in said rubber-reinforced vinyl aromatic (co)polymer, the rubber particles obtained by a continuous bulk process from a functionalized low cis polybutadiene rubber (LCBR) are obtained from a functionalized low cis polybutadiene rubber (LCBR) having the following characteristics: -Weight average molecular weight (M w ) is 40000 g / mol to 110000 g / mol, preferably 50000 g / mol to 100000 g / mol, more preferably 55000 g / mol to 95000 g / mol; - Polydispersity Index (PDI), i.e. weight average molecular weight (M w ) and number average molecular weight (M n ) ratio (M w / M n ) is 1.4 or less, preferably 1.3 or less, more preferably 1.2 or less; - isomeric components of double bonds in rubber chains (microstructure): 1,4-cis unit content is 10% by weight to 70% by weight, preferably 20% by weight to 60% by weight, more preferably 30% by weight to 50% by weight; 1,4-trans unit content is 20% by weight to 80% by weight, preferably 30% by weight to 70% by weight, more preferably 40% by weight to 60% by weight; 1,2-vinyl unit content is 0% by weight to 25% by weight, preferably 0% by weight to 20% by weight; more preferably 5% by weight to 15% by weight; The low cis polybutadiene rubber (LCBR) is functionalized with a functional group capable of promoting controlled chain radical polymerization mediated by a stable free nitroxyl radical; the low cis polybutadiene rubber (LCBR) has a functional group number per rubber polymer chain of 1 or less, preferably 0.05 to 1, more preferably 0.2 to 0.8, and even more preferably 0.3 to 0.7.

[0057] According to a preferred embodiment of the present invention, in said rubber-reinforced vinyl aromatic (co)polymer: - Weight average molecular weight (M w ) is 8000 g / mol to 70000 g / mol, preferably 10000 g / mol to 60000 g / mol, more preferably 15000 g / mol to 50000 g / mol; -Polydispersity index (PDI) of free functionalized low-cis polybutadiene rubber (LCBR), i.e., weight average molecular weight (M w ) and number average molecular weight (M n ) ratio (M w / M n ) is 1.3 or more, preferably 1.4 or more, more preferably 1.5 or more; The double bond isomer components (microstructure) of the free functionalized low cis polybutadiene rubber (LCBR) are: the content of 1,4-cis units is 10% by weight to 70% by weight, preferably 20% by weight to 60% by weight, more preferably 30% by weight to 50% by weight; the content of 1,4-trans units is 20% by weight to 80% by weight, preferably 30% by weight to 70% by weight, more preferably 40% by weight to 60% by weight; and the content of 1,2-vinyl units is 0% by weight to 25% by weight, preferably 0% by weight to 20% by weight; more preferably 5% by weight to 15% by weight.

[0058] According to a preferred embodiment of the present invention, in the rubber-reinforced vinyl aromatic (co)polymer, the weight average molecular weight (M w )(M w LCBR l , expressed in g / mol), the average volume diameter of the rubber particles (D vm , expressed in μm), and the volume of rubber particles with diameters larger than 0.40 μm (% particles >0.4μm ), the ratio of rubber particles containing blockages to rubber particles without blockages (ratio 閉塞部位 / 非閉塞部位 ), and the weight average molecular weight of the polymer matrix (M w )(M w SAN, expressed in g / mol), are related by the following relationship:

number

[0059] According to a preferred embodiment of the present invention, the rubber-reinforced vinyl aromatic (co)polymer has the following characteristics: a gloss value measured at -20° of 50 or more, preferably 55 or more, and more preferably 60 or more; a gloss sensitivity of 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less; Impact resistance measured at -23°C is 12kJ / m 2 More than 14 kJ / m 2 More preferably, 16 kJ / m 2 More than; a puncture resistance, calculated as the product of the displacement at break (expressed in mm) and the energy at break (expressed in J), of ≥ 400 J*mm, preferably ≥ 450 J*mm, more preferably ≥ 500 J*mm;

[0060] As mentioned above, the present invention also relates to a process for the preparation of the rubber-toughened vinyl aromatic (co)polymers reported above.

[0061] A further object of the present invention is therefore a process for the preparation of rubber-reinforced vinyl aromatic (co)polymers, which comprises the steps of: (a) Weight average molecular weight (M w obtaining a functionalized low-cis polybutadiene rubber (LCBR) having a molecular weight of 40,000 g / mol to 110,000 g / mol, preferably 50,000 g / mol to 100,000 g / mol, more preferably 60,000 g / mol to 95,000 g / mol; (b) discontinuously exchanging the low boiling point solvent with a vinyl aromatic monomer; (c) storing a solution of the functionalized low-cis polybutadiene rubber (LCBR) in a vinyl aromatic monomer in a buffer tank according to the grade of the functionalized low-cis polybutadiene rubber (LCBR) obtained; (d) delivering an aliquot of the solution of functionalized low-cis polybutadiene rubber (LCBR) in vinyl aromatic monomer stored in the buffer tank to a vessel, adding additional aliquots of vinyl aromatic monomer to obtain the desired rubber concentration in the reaction mixture, and adding at least one solvent, at least one free radical polymerization initiator, at least one chain transfer agent, and additional conventional additives; (e) continuously feeding the solution obtained in step (d) into a first plug flow reactor (PFR) (R1) and feeding a stream comprising at least one comonomer immediately before entering said first reactor (R1); (f) continuously feeding the reaction mixture leaving said first reactor (R1) into a second plug flow reactor (PFR) (R2), which is also continuously fed with a solution of at least one chain transfer agent in a solvent; (g) recovering the rubber-toughened vinyl aromatic (co)polymer from the polymerization plant; Weight average molecular weight (M) of functionalized low-cis polybutadiene rubber (LCBR) w ) (expressed in g / mol), the amount of chain transfer agent fed to the first plug flow reactor (PFR) (R1) [step (e)] (expressed in ppm, i.e. the amount by weight of chain transfer agent fed relative to the total weight of compounds fed in said [step (e)]), and the average volume diameter (expressed in μm) of the functionalized low-cis polybutadiene rubber (LCBR) particles are in the following relationship:

number

[0062] It is important to note that the above relationship:

number

[0063] Step (a) of the above process for obtaining functionalized low-cis polybutadiene rubber (LCBR) can be carried out as described in the art.

[0064] For this purpose, poly(1,3-alkadiene), preferably 1,3-polybutadiene, is obtained by anionic radical polymerization of at least one 1,3-alkadiene monomer, preferably 1,3-butadiene, in the presence of at least one aliphatic or cycloaliphatic low-boiling solvent or mixtures thereof and at least one initiator, preferably a lithium alkyl.

[0065] To ensure the properties of the functionalized low-cis polybutadiene rubber (LCBR) useful for the purposes of the present invention, the aforementioned polymerization is carried out in a batch type reactor, in which an initiator, usually primary or secondary lithium butyl, is added to a reaction mixture containing at least one aliphatic or cycloaliphatic low boiling solvent (e.g., cyclohexane) or mixtures thereof and at least one 1,3-alkadiene monomer, preferably 1,3-butadiene, in an amount such that at the end of the polymerization, the total amount of solids in the reaction mixture does not exceed 20% by weight relative to the total weight of the reaction mixture.

[0066] It is also known that the polymerization can be carried out in the presence of at least one Lewis base, more or less, depending on the content of 1,2-vinyl units obtained in the polymer chain. The Lewis base is generally chosen from ethers or tertiary amines, and in particular tetrahydrofuran (THF), already in an amount equal to 100 ppm on the solvent, can significantly accelerate the polymerization reaction while maintaining the content of 1,2-vinyl units at a level of less than 12% (molar). In the presence of larger amounts of tetrahydrofuran (THF), the microstructure changes gradually until the content of 1,2-vinyl units exceeds 40% [for example, in amounts equal to 5000 ppm of tetrahydrofuran (THF)]: large amounts of 1,2-vinyl units are not necessary, even if they are not harmful, when using polymers such as, for example, polybutadiene, in the field of plastic material modification, and for this purpose, it is preferable that the content of 1,2-vinyl units is less than or equal to 25%.

[0067] It is also known that polymerization reactions carried out in the absence of ethers or tertiary amines, controlled by the initial temperature of the reaction mixture, the final temperature of which does not exceed 120°C and in any case cannot be lower than 35°C-40°C, are rapid enough to ensure complete polymerization of the monomers in a time not exceeding one hour, but in this case the initiation rate of the reaction is insufficient and does not fit into the normal production cycles.

[0068] The polymerization carried out in a batch reactor is carried out to obtain a high degree of uniformity in the polydispersity index (PDI), i.e., the weight average molecular weight (M w ) and number average molecular weight (M n ) ratio (M w / M n ) determines the formation of a polymer with a monomodal molecular weight distribution very close to 1, generally between 1 and 1.2, and in any case not higher than 1.4.

[0069] The polymer obtained at the end of the polymerization is a linear polymer, with the polymer chain end groups still active, said end groups being constituted by lithium-polyalkadienyl species (polybutadienyl in the case of 1,3-butadiene monomer). The addition of protogenic agents (e.g. alcohols or carboxylic acids) or silicon aloderivatives with a halogen to silicon ratio equal to 1 (e.g. trimethylchlorosilane (TMCS)) determines the termination of the lithium-butadienyl end groups while preserving the linear macrostructure of the molecule.

[0070] Consequently, in order to deactivate the still active polymer chain end groups, at least one terminating agent is usually added, which is preferably selected from compounds having the general formula (I) or (II): [ka] (In the formula, R 1 is C1-C 18 represents an alkyl group); [ka] (In the formula, R 2 is C6-C 18 represents an alkyl group).

[0071] At the end of the aforesaid polymerization, a solution of low cis polybutadiene rubber (LCBR) in a low boiling aliphatic or cycloaliphatic solvent is obtained.

[0072] To functionalize the low cis polybutadiene rubber (LCBR), a catalytic polymerization system consisting of at least one free radical initiator (G) having functionality F capable of abstracting a proton from the polymer chain of the polybutadiene rubber and at least one stable free radical initiator containing a free nitroxyl radical (NO●) (III) is added to the solution, operating at a molar ratio of free nitroxyl radical (NO●) (III) / (G)*F smaller than 4, preferably between 1 and 2, where F is equal to the number of functional groups per molecule of the free radical initiator (G) and which generates two free radicals by decomposition.

[0073] The reaction mixture thus obtained is heated to a temperature at which dissociation of the radical initiator (G) occurs and maintained at said temperature for a time necessary for at least 95% of the stable free radical initiator, including the free nitroxyl radical (NO●) (III), to be bonded to the polymer chains of the low-cis polybutadiene rubber (LCBR).

[0074] For purposes of this invention, the number of moles of stable free radical initiator containing free nitroxyl radical (NO ) (III) bound per low cis polybutadiene rubber (LCBR), defined as NSG, is calculated according to the following formula:

number

[0075] The free radical initiator (G) capable of abstracting a proton from the polybutadiene rubber polymer chain can be selected, for example, from the following: azo derivatives, such as, for example, 4,4'-bis-(di-iso-butyronitrile), 4,4'-bis(4-cyanopentanoic acid), 2,2'-azobis(2-amidinopropane) dihydrochloride, or mixtures thereof; peroxides; hydroperoxides; percarbonates; peresters; persalts, such as, for example, persulfates (e.g., potassium persulfate, ammonium persulfate); or mixtures thereof. Preferably, the free radical initiator (G) is selected from, for example, tert-butyl isopropyl monoperoxycarbonate, tert-butyl 2-ethylhexyl monoperoxycarbonate, dicumyl peroxide, di-tert-butyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxyacetate, cumyl tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, dibenzoyl peroxide, or mixtures thereof.

[0076] The stable free radical initiator containing a free nitroxyl radical (NO●) (III) can be selected from those having the following general formula (IIIa): [ka] During the ceremony, R1, R2, R5 and R6 are the same or different from each other and are C1-C 20 alkyl group, linear or branched, substituted or unsubstituted alkyl-(C1-C4)-aromatic group; R3 and R4 are the same or different and are C1-C 20 Represents an alkyl group, a linear or branched, substituted or unsubstituted alkyl-(C1-C4)-aromatic group, or R3-CNC-R4 may be part of a cyclic structure, e.g. having 4 or 5 carbon atoms, optionally fused with an aromatic ring or a saturated ring containing 3 to 20 carbon atoms.

[0077] Further details regarding stable free radical initiators, including free nitroxyl radicals (NO●) (III), and processes for their preparation can be found, for example, in US Pat. No. 4,581,429.

[0078] For the purposes of the present invention, preferably, the stable free radical initiator containing a nitroxyl radical (NO●) (III) is selected from 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, 2,2,6.6-tetramethyl-1-piperidinyloxy (known under the trade name TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (known under the trade name 4OH-TEMPO), 1,1,3,3-tetraethylisoindoline-2-oxy (known under the trade name TEDIO); further details regarding said stable free radical initiators containing a free nitroxyl radical (NO●) (III) and their preparation processes can be found, for example, in patent application WO 2004 / 078720.

[0079] At the end of step (a), step (b) of exchanging the vinyl aromatic monomer for the low boiling solvent can be carried out as follows:

[0080] For this purpose, the low boiling solvent is removed and replaced with a vinyl aromatic monomer (e.g., styrene) to maintain a final concentration of the functionalized low cis polybutadiene rubber (LCBR) in styrene of 5% to 45% by weight, preferably 5% to 40% by weight, more preferably 5% to 35% by weight, based on the total weight of the functionalized low cis polybutadiene rubber (LCBR) in styrene.

[0081] As reported above, in step (d), to the solution of functionalized low-cis polybutadiene rubber (LCBR) in vinyl aromatic monomer obtained in step (b), after storage in a buffer tank [step (c)], further aliquots of vinyl aromatic monomer are added to obtain the desired concentration of rubber in the reaction mixture, at least one solvent, at least one radical polymerization initiator, at least one chain transfer agent and further conventional additives are added.

[0082] The vinyl aromatic monomer (eg styrene) can be selected from those reported above.

[0083] According to a preferred embodiment of the present invention, in said step (d), the solvent may be selected from aromatic solvents, such as, for example, ethylbenzene, toluene, xylene or mixtures thereof; or aliphatic solvents, such as, for example, hexane, cyclohexane or mixtures thereof; or mixtures thereof. Ethylbenzene is preferred.

[0084] According to a preferred embodiment of the present invention, in step (d), the at least one radical initiator may be added in an amount of 0 wt.% to 0.7 wt.%, preferably 0 wt.% to 0.6 wt.%, more preferably 0.02 wt.% to 0.5 wt.%, based on the total weight of the reaction mixture.

[0085] According to a preferred embodiment of the present invention, in step (d), the at least one radical initiator may be selected from, for example, 4,4'-bis-(di-iso-butyronitrile), 4,4'-bis(4-cyanopentanoic acid), 2,2'-azobis(2-amidinopropane) dihydrochloride; peroxides; hydroperoxides; percarbonates; peresters; or mixtures thereof, having an activation temperature of 40°C to 170°C, preferably 50°C to 150°C, more preferably 70°C to 140°C. Preferably, the at least one radical initiator is selected from peroxides such as, for example, tert-butyl-iso-propyl monoperoxycarbonate, tert-butyl 2-ethylhexyl monoperoxycarbonate, dicumyl peroxide, di-tert-butyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane (di-tert-butylperoxycyclohexane), tert-butyl peroxyacetate, cumyl tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, or mixtures thereof.

[0086] According to a preferred embodiment of the present invention, in step (d), the at least one chain transfer agent can be added in an amount of 0.01% to 1% by weight, preferably 0.1% to 0.8% by weight, more preferably 0.15% to 0.6% by weight, based on the total weight of the reaction mixture.

[0087] According to a preferred embodiment of the present invention, in step (d), the at least one chain transfer agent may be selected from mercaptans such as, for example, n-octyl mercaptan, n-dodecyl mercaptan (NDM), tert-dodecyl mercaptan, mercaptoethanol or mixtures thereof. n-Dodecyl mercaptan (NDM) is preferred.

[0088] Further conventional additives that may be added in step (d) may be selected, for example, from antioxidants, UV stabilizers, plasticizers, demolding agents, isothermal additives, flame retardants, foaming agents, antistatic agents, dyes, stabilizers, and are appropriate and different depending on the application of the resulting rubber-reinforced vinyl aromatic (co)polymer.

[0089] According to a preferred embodiment of the present invention, the step (d) can be carried out at a temperature of 30°C to 90°C, preferably 40°C to 80°C.

[0090] According to a preferred embodiment of the present invention, in step (e), the at least one comonomer may be added in an amount of 5% by weight to 35% by weight, preferably 10% by weight to 30% by weight, more preferably 17% by weight to 27% by weight, based on the total weight of the reaction mixture.

[0091] According to a preferred embodiment of the present invention, the step (e) can be carried out at a temperature of 100°C to 130°C, preferably 110°C to 125°C.

[0092] In said step (f), said at least one chain transfer agent may be selected from those reported above.

[0093] According to a preferred embodiment of the present invention, in step (f), the at least one chain transfer agent may be added in an amount of 0.5 wt. % to 2.5 wt. %, preferably 0.7 wt. % to 2.2 wt. %, more preferably 0.9 wt. % to 2 wt. %, based on the total weight of the reaction mixture.

[0094] According to a preferred embodiment of the present invention, the step (f) can be carried out at a temperature of 120°C to 160°C, preferably 130°C to 155°C.

[0095] The process object of the present invention can be advantageously carried out in a continuous bulk polymerization plant to obtain the desired rubber-reinforced vinyl aromatic (co)polymers: further details regarding said plants are described, for example, in EP 0 400 479 B1.

[0096] In order that the present invention may be better understood and put into practice, some illustrative and non-limiting examples are given below. EXAMPLES

[0097] The analytical and characterization methods reported below were used.

[0098] a) Measurement of molecular weight distribution (MWD) Molecular weight distribution (MWD) measurements were performed by gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), by passing a tetrahydrofuran (THF) solution of the (co)polymer to be analyzed through a series of columns containing a solid phase made of cross-linked polystyrene with pores of different sizes.

[0099] The equipment used consisted of: -Waters 2695 injector pump system; - Waters 2414 refractive index detector ("RI detector"); -UV / Vis Waters 2489 detector.

[0100] The analysis was performed using four Phenogel columns with 5 μm particle size and variable porosity: 3 , 10 4 , 10 5 , 10 6A was used. The (co)polymer samples to be analyzed were dissolved in tetrahydrofuran (THF) to a concentration of 1 mg / mL for functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) and 2.5 mg / mL for free styrene-acrylonitrile (SAN) copolymer for at least 5 h and then filtered through a 0.45 μm polytetrafluoroethylene (PTFE) filter. The analysis was performed at 1 mL / min with tetrahydrofuran (THF) as the eluent.

[0101] This device measures the weight average molecular weight (M w ) was calibrated using 30 monodisperse polystyrene (PS) standards ranging from 7 million to 1000 daltons.

[0102] To determine the molecular weights of functionalized and non-functionalized low cis polybutadiene rubber (LCBR) and free styrene-acrylonitrile (SAN) copolymers, the theory of universal calibration according to the Mark-Houwink equation was referenced using the constants given in the table below: [Table 1]

[0103] References (i) Mori S. and Barth, HG in “Size Exclusion Chromatography” (1999), pg. 199-229, Springer Ed.; (ii) Evans JM, in “Polymer Engineering and Science” (1973), Vol. 13(6), pg. 401-408; (iii) Hamielec AE, MacGregor JF, Garcia Rubio, LH in “Advanced in Chemistry Series” (1963), Vol. 203, pg. 311-344.

[0104] Waters Empower2 software was used for acquisition and processing of chromatograms. Molecular weights were calculated using chromatograms obtained with the RI detector.

[0105] The weight average molecular weight (M) of non-functionalized low-cis polybutadiene rubber (LCBR) w ) was also determined for a sample of the rubber in cyclohexane taken after the termination reaction. The sample was dried (cyclohexane was slowly removed) and the dry residue was dissolved in tetrahydrofuran (THF) at room temperature (25° C.) for at least 4 hours using toluene as an internal standard.

[0106] Weight average molecular weight (M) of functionalized low-cis polybutadiene rubber (LCBR) w ) was also determined for a sample of the rubber in cyclohexane taken after the functionalization reaction. The sample was dried (cyclohexane was slowly removed) and the dry residue was dissolved in tetrahydrofuran (THF) at room temperature (25° C.) for at least 4 hours using toluene as an internal standard.

[0107] The weight average molecular weight (M) of both functionalized and non-functionalized free low-cis polybutadiene rubber (LCBR) in the resulting reinforced vinyl aromatic copolymer acrylonitrile-butadiene-styrene (ABS) was w ) was determined on samples of acrylonitrile-butadiene-styrene (ABS) copolymers obtained by method f) separation of functionalized and non-functionalized free low cis polybutadiene rubber (LCBR) in said copolymers by dissolving said samples in tetrahydrofuran (THF) at room temperature (25° C.) for at least 4 hours using toluene as an internal standard, as reported below.

[0108] Weight average molecular weight (M) of free styrene-acrylonitrile (SAN) copolymer w) was performed on samples obtained by method e) Determination of the swelling index of acrylonitrile-butadiene-styrene (ABS) copolymers reported below, by dissolving the sample in tetrahydrofuran (THF) at room temperature (25°C) for at least 4 hours, using toluene as the internal standard.

[0109] b) Determination of the microstructure of both functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers, and determination of the microstructure of both functionalized and non-functionalized free low-cis polybutadiene rubber (LCBR). The microstructural determination of functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers, as well as the microstructural determination of functionalized and non-functionalized free low-cis polybutadiene rubber (LCBR), was carried out using a Bruker Avance 300 MHz spectrometer with a probe temperature of 300 K (26.85 °C).

[0110] Samples were prepared as follows: Approximately 100 mg of sample was weighed on an analytical balance (sample obtained as described above) and transferred to a 10 mm diameter borosilicate NMR tube (Wilmad®). Approximately 3 mL of deuterated chloroform (CDCl3) (Sigma-Aldrich 99.96 atom % D+TMS ~ 0.1% v / v) was then added to obtain a viscous suspension, which was then heated to 50 °C on a hot plate and maintained at that temperature for 2 h until complete dissolution.

[0111] Two NMR spectra were then recorded, one proton and one carbon-13. The acquisition parameters are given in the table below: [Table 2]

[0112] The obtained FID was processed by Fourier transformation with zero-filling correction (SI: 128k). 1H-NMR spectra were processed without FID apodization (WDW:no). 13 C-NMR spectra were processed with exponential multiplicative apodization (WDW:EM) and line broadening of 2.0 Hz.

[0113] Phase correction can be done automatically or manually, and the baseline can be optimized by software algorithms. Chemical shift values ​​are based on the singlet resonance of tetramethylsilane (TMS) at 0.000 ppm ( 1 H-NMR spectrum and 13 The references are both C-NMR spectra.

[0114] To determine the complete microstructure of functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) samples in acrylonitrile-butadiene-styrene (ABS) copolymers, the proton spectra must be processed to obtain the mole percent quantification of 1,2 butadiene groups (1,2 vinyl units) and 1,4 butadiene (1,4-cis and 1,4-trans units) and the isomerization of 1,4-cis and 1,4-trans units is essential. 13 Both the processing of the C-NMR spectrum are necessary.

[0115] 1 The processing of H-NMR spectra was carried out according to the ISO21561-1:2015 standard (mainly applicable to styrene-butadiene polymers, but only applicable to the microstructural analysis of polybutadiene). In particular, by integrating the resonances at 4.97 ppm (signals designated by the letter A in the formulas reported below: integration range is 4.80-5.15 ppm) and 5.42 ppm (signals designated by the letter B in the formulas reported below: integration range is 5.20-5.75 ppm), it is possible to calculate the total mole percent distribution of 1,2 butadiene (1,2 vinyl units) and 1,4 butadiene (1,4-cis and 1,4-trans units) groups according to formulas (1) and (2):

number

[0116] The ratio of 1,4-cis units and 1,4-trans units was determined by the relative integrals of two signals (24.90 ppm and 27.42 ppm) referring to the methylene carbons adjacent to the double bonds in the cis configuration and two signals (30.15 ppm and 32.71 ppm) referring to the methylene carbons adjacent to the double bonds in the trans configuration, according to the following equations (3) and (4), as reported in the literature by Sato H., Takebayashi K., Tanaka Y., in “Macromolecules” (1987), Vol. 20, pg. 2418-2423: 13 C-NMR spectroscopy was used:

number

[0117] c) Determination of functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) concentrations in styrene The concentration of both functionalized and non-functionalized low cis butadiene rubber (LCBR) in the styrene obtained at the end of step (b) of the process objective of the present invention (exchange of styrene with a low boiling non-polar solvent) was measured by thermogravimetry using a Sartorius Model MA50 thermobalance.

[0118] For this purpose, 3 g of functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) in styrene were placed in a pre-calibrated vessel and heated to 200° C. for 30 min to remove the styrene. After cooling, the vessel with the dry residue was weighed and the percentage of both functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) was determined by the ratio of the two weighed amounts (dry / solution).

[0119] d) Determination of the concentration of both functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers. The concentration of functionalized low-cis-butadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers was determined by iodometric titration according to the method reported by Wys JJA, in “Berichte” (1898), Vol. 31, pg. 750-752.

[0120] e) Measurement of swelling index The degree of crosslinking of the rubber phase (ie, rubber particles) in acrylonitrile-butadiene-styrene (ABS) copolymers was determined by measuring the swelling index value of the copolymer.

[0121] For this purpose, the following process was carried out: two 50 mL steel centrifuge tubes were prepared, each containing 0.5 g of acrylonitrile-butadiene-styrene (ABS) copolymer and 25 mL of acetone; the tubes were left overnight at room temperature (25 °C) to allow complete dissolution. After mixing the solution with a rod, the volume was made up to about 30 mL with acetone and the whole was centrifuged at 20000 rpm (45000 g) for 20 min using a Sorvall Evolution RC laboratory ultracentrifuge equipped with a SA300 rotor. At the end of the centrifugation, the supernatant was decanted and the weight average molecular weight (M) of the free styrene-acrylonitrile copolymer was measured, as reported below. w ) were saved for analysis.

[0122] After removing the acetone, the gummy phase stuck at the bottom of the tube was diluted by adding 10 mL of tetrahydrofuran (THF) to bring the volume to approximately 30 mL with tetrahydrofuran (THF), the whole was centrifuged at 20,000 rpm (45,000 g) for 20 min, and the resulting supernatant was decanted.

[0123] At the same time, the weight of a crucible with a dry porous filter Gooch septum, which had been immersed for at least 1 h in a container with tetrahydrofuran (THF), was measured (first weight = P1): the height of the tetrahydrofuran (THF) was equal to the height of the porous septum of the crucible, and the container was kept in a closed container. The crucible was then extracted and allowed to dry on the glass wall without allowing the solvent to come into contact with the wet porous septum, and the whole was quickly weighed (second weight = P2).

[0124] The solid residues deposited on the porous partition of the crucible were collected from the two test tubes using a spatula without touching the walls and dispersed so as to completely cover the porous partition: the whole was left to swell for 5 hours in a closed container at room temperature (25°C). The crucible was removed again, the solvent adhering to the glass wall was allowed to dry without touching the wet porous partition or the solids deposited on it, and the whole was quickly weighed again (third weight = P3).

[0125] At this point, ethanol was added drop by drop to the solid residue present in the crucible until it was completely filled, and the whole was filtered. The solid residue remaining in the crucible was dried in an oven at 40° C. under vacuum for 12 hours: finally, the weight of the crucible containing the dried gel was measured (fourth weight=P4).

[0126] The swelling index value was calculated according to the following formula (5):

number

[0127] The supernatant obtained after the first centrifugation was treated as follows: Method a) Determination of molecular weight distribution (MDW) was operated as described above, and after complete removal of acetone, the solid residue obtained was dissolved in a minimum amount of tetrahydrofuran (THF), reprecipitated in ethanol, subjected to filtration, dried in an oven at 40° C. under vacuum for 12 hours, and then subjected to gel permeation chromatography (GPC).

[0128] f) Separation of functionalized and non-functionalized free low-cis polybutadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers The weight average molecular weight (M) of both functionalized and non-functionalized low-cis polybutadiene rubber (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers w ) and microstructure were determined by modifying the process reported in the literature by Turner RR, Carlson DW, Altenau AG, in “Journal of Elastomers and Plastics” (1974), Vol. 6, pg. 94-102.

[0129] For this purpose, eight 50 mL steel centrifuge tubes were prepared, each containing 0.5 g of acrylonitrile-butadiene-styrene (ABS) copolymer and 25 mL of acetone: the tubes were left overnight to completely dissolve at room temperature (25 °C). After mixing the solution with a rod, the volume was made up to about 30 mL with acetone and the whole was centrifuged at 20000 rpm (45000 g) for 30 min using a Sorvall Evolution RC laboratory ultracentrifuge equipped with a SA300 rotor. After the end of the centrifugation, the supernatant was decanted. After removing the acetone, the rubber phase stuck at the bottom of the tube was diluted by adding 10 mL of acetone, the volume was made up to about 30 mL with acetone, the whole was centrifuged at 20000 rpm (45000 g) for 30 min and the resulting supernatant was decanted: this process was repeated twice. The solid residue (rubber phase) that had settled at the bottom of the tube was collected and placed in the thimble of a Kumagawa extractor. 200 mL of cyclohexane was added to the extractor and the whole was refluxed for 24 hours. The cyclohexane solution was dried by evaporating the cyclohexane, and the resulting solid residue was analyzed for its weight average molecular weight (M wThe samples were subjected to gel permeation chromatography (GPC) operating as described above in the method a) for the determination of the molecular weight distribution (MWD) and b) for the determination of the microstructure of both functionalized and non-functionalized low cis polybutadiene rubbers (LCBR) in acrylonitrile-butadiene-styrene (ABS) copolymers and to NMR analysis operating as described above in the method reported in the determination of the microstructure of both functionalized and non-functionalized free low cis polybutadiene rubbers (LCBR).

[0130] g) Transmission electron microscopy (TEM) and image analysis The particle size and rubber phase volume of low-cis polybutadiene rubber (LCBR) were measured by transmission electron microscopy (TEM).

[0131] For this purpose, a sample (granules) of styrene-butadiene-acrylonitrile (ABS) copolymer was placed in a clamp and appropriately trimmed to prepare a suitable surface for subsequent ultrathin sectioning. The sample was then immersed in a 4% solution of osmium tetroxide (OsO4) (Sigma-Aldrich) for about 48 hours at room temperature (25 °C) ("staining"). After this treatment, the sample was hard enough to be sectioned by ultrathin sectioning at room temperature (25 °C), yielding sections with a thickness of about 120 nm (determined by the interference color that occurs on the water surface after the sections are cut). The sections were collected on copper grids and observed in a transmission electron microscope TEM PHILIPS CM120 at 80 KV.

[0132] A series of images of the sample were then digitized at 1:1 magnification in order to obtain a statistically significant number of counted particles (usually around 1000). The images were analyzed using the AnalySIS image analysis software: image analysis allows the extraction of numerical parameters from the images, such as area, perimeter, diameter, extinction, optical density, transmittance, topological parameters, etc. This is done using mathematical algorithms that allow obtaining information from images that have been simplified into numerical form by suitable acquisition and processing systems. The image analysis to numerically determine the dispersed rubber phase was carried out as described in US Pat. No. 7,115,684 (column 11, line 22 to column 13, line 65). In particular, the values ​​of "dispersion coefficient I" reported in Tables 2a to 2d were determined as described in the aforementioned US Pat. No. 7,115,684, column 13, lines 54 to 60, while the average volume diameter of the rubber particles was determined as described in the aforementioned US Pat. No. 7,115,684, column 13, lines 35 to 30.

[0133] All images and raw data were stored and available for further processing of stereological properties aimed at reconstructing the actual diameter and volume distribution of particles in a styrene-butadiene-acrylonitrile (ABS) copolymer sample.

[0134] h) Determination of the ratio of rubber particles containing blockages to rubber particles without blockages The ratio of rubber particles without obstructions (hereafter referred to as balls) to those containing obstructions (hereafter referred to as caps and “salami”) is predicated a priori on the overall count of particles performed by transmission electron microscopy (TEM) and image analysis reported above.

[0135] In particular it is defined as follows: -Ball: rubber particles without matrix blockages inside; - Cap: a rubber particle in which a single matrix occlusion occupies an area equivalent to at least 85% of the total surface area of ​​the particle itself; - "Salami": a rubber particle containing two or more matrix occlusions; in this type of particle, no matrix occlusion occupies an area of ​​more than 85% of the total surface of the particle itself.

[0136] Blockages are characterized by a light-colored, occluded area of ​​at least 0.01 μm 2 The surface is identified as being

[0137] In order to define the relationship between rubber particles without obstructions (balls) and those with obstructions [caps and “salami”], particle types with the morphology defined above were highlighted in different colors on the images obtained as described above.

[0138] This analysis is also performed on a statistically significant number of particles (usually around 1000). In the calculation stage, the software can process and perform the analysis monochromatically, calculating the data, percentages and relative proportions for each type of particle identified. The percentages of the various types of particles are expressed relative to the total particles analyzed, and represent the number of particles of a particular type relative to the total.

[0139] The ratio of particles with and without occlusions is defined as:

number

[0140] Also in this case, the images and data are stored for further processing.

[0141] i) Melt Flow Index (MFI) Measurement The melt flow index (MFI) was measured at 220°C under a load of 10 kg according to the ISO1133-1:2011 standard.

[0142] l) IZOD measurement (impact resistance) Notched Izod values ​​(on injection moulded specimens according to ISO294:1-2017 standard) are measured according to ISO180 / 1A-2020 and are expressed in kJ / m 2This is expressed as:

[0143] m) Tensile strength Tensile strength properties (injection molded specimens according to ISO294:1-2017 standard) were measured according to ISO527-1:2019 standard and values ​​are expressed as shown below: - Elastic modulus: MPa; - Yield stress: MPa; - Stress at break: MPa; - Yield point elongation: %; Elongation at break: %

[0144] n) Gloss measurement The gloss of styrene-butadiene-acrylonitrile (ABS) copolymers was measured according to the ASTM D523-14:2018 standard using a BYG Gardner Model 4563 gloss meter at a reading angle of 20°.

[0145] The measurements were carried out on "3-step" specimens (see Figure 1 showing the dimensions of the "3-step" plate for measuring the gloss @ 20° of the obtained copolymers) obtained by injection moulding according to the ISO 294:1-2017 standard, using a Negri & Bossi model NB60 injection moulding machine. In particular, the gloss measurements were carried out in the central part of the plate (2nd step, dimensions 93 x 75 x 3 mm) at the height of the injection point. The measured gloss value is the average reading of at least 10 samples operated under the following conditions: -Melting temperature: 240℃; -Molding temperature: 25℃.

[0146] o) Measurement of gloss sensitivity Gloss sensitivity measurements were performed according to the ASTM D523-14:2018 standard using a GARD PLUS Model 4725 gloss meter at a reading angle of 20°.

[0147] The measurements were carried out on flat specimens with dimensions 60 x 60 x 3 mm, injection moulded according to standard ISO 294-3:2002 using an ENGEL model ES150 / 50 injection moulding machine.

[0148] Different point gloss values ​​were measured in the center of the printing plate under the following different operating conditions (average value of at least 10 samples): -Melting temperature: 240℃; -Injection speed: 100mm / s or 300mm / s; -Molding temperature: 30℃ or 60℃.

[0149] Once the injection speed was determined (e.g. 100 mm / s), ten plates were molded for different mold temperatures (30°C or 60°C). The same operation was repeated with different injection speeds. Thus, a 2×2 matrix of values ​​was defined according to the following equation (11):

number

[0150] The gloss sensitivity value is defined by the following formula (12):

number

[0151] p) Biaxial bending test (puncture resistance) Biaxial bending measurements (puncture resistance) were performed with an INSTRON model 4400R universal testing machine (with Bluehill 2.35 control software) with an upper movable crosshead according to the ISO 7500-1:2018 standard: the universal testing machine was able to maintain a constant crosshead speed equal to 50 mm / min with a tolerance of ±10% during the test. The universal testing machine was equipped with a punch with a hemispherical head with a radius of curvature R = 10 mm and a circular support with an outer diameter equal to 148 mm to support the specimen. On the upper surface of the support there was a housing with a diameter of 85 mm concentric with the support: this housing was useful to keep the specimen in the correct position. The circular support was also provided with a concentric hole with a diameter of 40 mm to allow deformation of the specimen during the test. The punch was inserted and fixed in the moving crosshead and the circular support was fixed on the base plate of the universal testing machine so that the vertical axis of the punch and the vertical axis of the circular support coincided.

[0152] The test geometry used is shown in Figure 2: below is a side view showing the hemispherical head punch; above is a top view (dimensions in mm) ("Provino" = "test specimen"). The biaxial bending geometry shown in Figure 2 determines a very complex stress state in the specimen during the test: in fact, by separating the stresses into radial, circumferential and normal components (in a coordinate system with the origin placed at the center of the specimen and the normal axis parallel to the thickness of the specimen), biaxial traction occurs at the center of the face facing the mounting punch, biaxial compression occurs at the center of the face in contact with the punch, circumferential stresses increase towards the circular support, radial stresses decrease and shear stresses occur. Due to this complexity of the stress state occurring in the specimen, it is convenient to use isotropic specimens or specimens in which the state of molecular orientation (e.g. due to injection molding) is as geometrically simple and controllable as possible and does not depend too much on the thermal and rheological properties of the material. For this purpose, injection-molded specimens were used, consisting of a square plate of size 60 x 60 x 2 (mm) molded according to the ISO 294-3:2002 standard. The injection molding conditions were selected according to the ISO 19062-2:2019 standard: The specimen thus obtained was placed in a housing of the lower support so that the punch could penetrate its centre: The upper punch was fixed to the crosshead and moved at a speed of 50 mm / min. The universal testing machine software acquired and plotted the data of load (N) versus displacement (mm), and the following output parameters were obtained from each test run: - Displacement at break (mm): the value of the crosshead displacement corresponding to the point at which the onset of specimen breakage is detected (the onset of specimen breakage is detected when the drop in the force measured between two consecutive acquisition points is more than 20%); - Strength at break (N): the force value at which the onset of fracture of the test specimen is detected (see above); -Energy at fracture (J): The value of the area of ​​the entire curve up to the initiation of fracture, which represents the deformation energy of the test piece up to the initiation of fracture.

[0153] As reported above, the puncture resistance is calculated as the product of the displacement at break (expressed in mm) and the energy at break (expressed in J), and the unit of measurement is J*mm.

[0154] As mentioned above, the present invention also relates to a process for the preparation of rubber-toughened vinyl aromatic (co)polymers.

[0155] As an example, some test results are shown in FIG. 3, where the solid line indicates Example 3 (comparative example), the dashed line indicates Example 8 (comparative example), and the dashed points indicate Example 9 (inventive example).

[0156] Table A below provides a list of the reagents used in the following examples, along with their characteristics and suppliers.

[0157] [Table 3] [Brief description of the drawings]

[0158] [Figure 1] FIG. 1 shows the dimensions of the "3-step" plate for measuring the gloss of copolymers. [Diagram 2] FIG. 1 is a diagram showing a biaxial bending shape in a biaxial bending measurement (puncture resistance). [Diagram 3] FIG. 1 is a diagram showing test results of Example 3 (Comparative Example), Example 8 (Comparative Example) and Example 9 (Inventive Example).

[0159] Example 1 (Comparative Example) A 50 liter vessel equipped with an agitator was charged with: 21.4 Kg of styrene, 3.7 Kg of ethylbenzene, 4.9 Kg of SBR Europrene® SOL B183 rubber, 11.5 g of 1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator) and 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant). The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a first 10 liter plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. Just before entering the first plug flow reactor (PFR) (R1), a stream of acrylonitrile was added to the solution at a flow rate of 0.7 Kg / h. The temperature profile of the reactor was increased from 113°C to 122°C, and the stirring speed was kept constant at 80 rpm. In the first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. To the mixture leaving the first plug flow reactor (PFR) (R1), a solution of n-dodecyl mercaptan (NDM) (chain transfer agent) in ethylbenzene (EB) [60.0 g of NDM in 0.940 kg of EB, corresponding to a concentration of 6.0% NDM in ethylbenzene] was continuously added (0.15 Kg / h) and fed to a second plug flow reactor (PFR) (R2), also equipped with an agitator and a temperature control system, and the temperature profile of the reactor was increased from 139°C to 150°C, and the stirring speed was kept constant at 10 rpm.

[0160] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1a. The characteristics of the product obtained are shown in Table 2a.

[0161] Example 2 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 1208.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 115° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of ethanol equivalent to 22.0 g was also fed to complete the termination of the chain ends.

[0162] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 60,206 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0163] The reaction mixture containing low-cis polybutadiene rubber (LCBR) and cyclohexane obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 313.1 Kg of condensate was collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 26.8%.

[0164] An aliquot equivalent to 16.6 Kg of low-cis polybutadiene rubber (LCBR) 26.8% in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 9.7 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant). The solution thus obtained was fed continuously at a flow rate of 3.8 Kg / h to a first 10 liter plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [60.0 g of NDM in 0.940 kg of EB corresponds to a concentration of 6.0% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0165] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1a. The characteristics of the product obtained are shown in Table 2a.

[0166] Example 3 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket with circulating diastere oil at 50° C., was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 967.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, the reaction mixture was fed at a temperature of 113° C. to a second reactor of 300 liters equipped with an agitator and a heating jacket with circulating diastere oil at 25° C., and an aliquot equivalent to 51.0 g of heptanoic acid was fed to complete the termination of the chain ends.

[0167] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which revealed a weight average molecular weight value (M) of 77,561 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0168] The reaction mixture containing low cis butadiene rubber (LCBR) and cyclohexane obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the condensate recovery system confirmed the presence of liquid, 248.8 Kg of styrene was slowly added, while the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 301.2 Kg of condensate was collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of low cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 23.4%.

[0169] An aliquot corresponding to 19.0 Kg of a 23.4% low-cis polybutadiene rubber (LCBR) solution in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 7.3 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant). The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0170] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1a. The characteristics of the product obtained are shown in Table 2a.

[0171] Example 4 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 806.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 111° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of heptanoic acid equivalent to 42.0 g was also fed to complete the termination of the chain ends.

[0172] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 91,586 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0173] The reaction mixture containing low-cis polybutadiene rubber (LCBR) and cyclohexane obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the condensate recovery system confirmed the presence of liquid, 248.8 Kg of styrene was slowly added, while the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 289.4 Kg of condensate was collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 20.8%.

[0174] An aliquot equivalent to 21.4 Kg of low-cis polybutadiene rubber (LCBR) 20.8% in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 4.9 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant). The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a first 10 liter plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0175] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1a. The characteristics of the product obtained are shown in Table 2a.

[0176] Example 5 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 1208.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 115° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of heptanoic acid equivalent to 64.0 g was also fed to complete the termination of the chain ends.

[0177] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 59731 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0178] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 38.1 g of dibenzoyl peroxide [Perkadox 1-W75 (BPO)] and 31.5 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105°C and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0179] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 59,254 g / mol. w ) and a polydispersity index (PDI) value (M w / Mn ) was obtained.

[0180] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 315.2 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 27.5%.

[0181] An aliquot corresponding to 16.2 Kg of 27.5% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 10.1 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 9.3 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [54.0 g of NDM in 0.946 kg of EB corresponds to a concentration of 5.4% of NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0182] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1b. The characteristics of the product obtained are given in Table 2b.

[0183] Example 6 (present invention) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 1208.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 115° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of ethanol equivalent to 22.0 g was also fed to complete the termination of the chain ends.

[0184] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which gave a weight average molecular weight value t(M w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0185] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 38.1 g of dibenzoyl peroxide [Perkadox 1-W75 (BPO)] and 31.5 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105°C and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0186] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 61,256 g / mol. w ) and a polydispersity index (PDI) value (M w / Mn ) was obtained.

[0187] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 313.7 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 27.0%.

[0188] An aliquot equivalent to 16.5 Kg of 27.0% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with: 9.8 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 17.0 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0189] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1b. The characteristics of the product obtained are given in Table 2b.

[0190] Example 7 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 1208.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 115° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of ethanol equivalent to 22.0 g was also fed to complete the termination of the chain ends.

[0191] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 60,986 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0192] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 38.1 g of dibenzoyl peroxide [Perkadox 1-W75 (BPO)] and 31.5 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105°C and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0193] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 60138 g / mol. w ) and a polydispersity index (PDI) value (M w / Mn ) was obtained.

[0194] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 314.6 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 27.3%.

[0195] An aliquot equivalent to 16.3 Kg of 27.3% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with: 10.0 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 22.2 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [39.0 g of NDM in 0.961 kg of EB corresponds to a concentration of 3.9% of NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0196] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1b. The characteristics of the product obtained are given in Table 2b.

[0197] Example 8 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 967.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 113° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of ethanol equivalent to 18.0 g was also fed to complete the termination of the chain ends.

[0198] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which revealed a weight average molecular weight value (M) of 73,791 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0199] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 30.5 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 25.2 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0200] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 73,578 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0201] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 303.9 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 24.1%.

[0202] An aliquot corresponding to 18.5 Kg of 24.1% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with: 7.8 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 5.6 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0203] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1c. The characteristics of the product obtained are given in Table 2c.

[0204] Example 9 (Invention Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 967.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 113° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of ethanol equivalent to 18.0 g was also fed to complete the termination of the chain ends.

[0205] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 78,736 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0206] To the reaction mixture containing the polybutadiene (LCBR) obtained above and cyclohexane, 30.5 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 25.2 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low-cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0207] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 78,201 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0208] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 298.7 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 22.8%.

[0209] An aliquot corresponding to 19.5 Kg of 22.8% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with: 6.8 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of 1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 13 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was fed continuously at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [39.0 g of NDM in 0.961 kg of EB corresponds to a concentration of 3.9% of NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0210] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1c. The characteristics of the product obtained are given in Table 2c.

[0211] Example 10 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 967.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 113° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of heptanoic acid equivalent to 51.0 g was also fed to complete the termination of the chain ends.

[0212] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 77,568 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0213] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 30.5 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 25.2 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0214] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 77,853 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0215] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed by the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 302.0 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 23.7%.

[0216] An aliquot corresponding to 19.2 Kg of 23.7% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with: 7.4 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 16.7 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [33.0 g of NDM in 0.967 kg of EB corresponds to a concentration of 3.3% of NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0217] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1c. The characteristics of the product obtained are given in Table 2c.

[0218] Example 11 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 806.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 113° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot equivalent to 15.0 g of ethanol was also fed to complete the termination of the chain ends.

[0219] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 89,882 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0220] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 25.4 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 21.0 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0221] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 90026 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0222] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the condensate recovery system confirmed the presence of liquid, 248.8 Kg of styrene was slowly added, while the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 291.4 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 21.2%.

[0223] An aliquot corresponding to 21.0 Kg of functionalized low-cis polybutadiene rubber (LCBR) at 21.2% in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 5.3 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 5.6 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0224] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are given in Table 1d. The characteristics of the product obtained are given in Table 2d.

[0225] Example 12 (Invention Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 806.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 110° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of heptanoic acid equivalent to 42.0 g was also fed to complete the termination of the chain ends.

[0226] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 90,566 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0227] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 25.4 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 21.0 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0228] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 89,823 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0229] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 292.9 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 21.5%.

[0230] An aliquot corresponding to 20.7 Kg of 21.5% functionalized low-cis polybutadiene rubber (LCBR) in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 5.6 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 9.3 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was continuously fed at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [45.0 g of NDM in 0.955 kg of EB corresponds to a concentration of 4.5% NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0231] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1c. The characteristics of the product obtained are shown in Table 2d.

[0232] Example 13 (Comparative Example) A 300 liter reactor, kept anhydrous and equipped with an agitator and a heating jacket in which diacetate oil at 50° C. is circulated, was fed in a nitrogen stream with the following in turn: 124.4 Kg of anhydrous cyclohexane, 22.0 Kg of anhydrous butadiene free of inhibitors and acetylenic hydrocarbons, and when the reaction mixture reached a temperature of 40° C., 806.0 g of a solution of n-butyllithium (nBL) in cyclohexane (2% by weight) was fed. Upon complete conversion, at a temperature of 110° C., the reaction mixture was fed to a second reactor of 300 liters equipped with an agitator and a heating jacket in which diacetate oil at a temperature of 25° C. was circulated, and an aliquot of heptanoic acid equivalent to 42.0 g was also fed to complete the termination of the chain ends.

[0233] A sample of low-cis polybutadiene rubber (LCBR) was subjected to a measurement of the molecular weight distribution carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 91,156 g / mol. w ) and a polydispersity index (PDI) value (M w / M n ) was obtained.

[0234] To the reaction mixture containing the low cis polybutadiene rubber (LCBR) obtained above and cyclohexane, 25.4 g of dibenzoyl peroxide [Perkadox1-W75 (BPO)] and 21.0 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO) were added: the mixture thus obtained was incubated at a temperature of 105° C. and kept at said temperature for 3 hours under stirring until the low cis polybutadiene rubber (LCBR) chains were fully functionalized with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4OH-TEMPO).

[0235] A sample of the functionalized low-cis polybutadiene rubber (LCBR) was subjected to a molecular weight distribution measurement carried out by gel permeation chromatography (GPC) operating as reported above, which showed a weight average molecular weight value (M) of 90,992 g / mol. w ) and a polydispersity index (PDI) value (M w / M n) was obtained.

[0236] The solution of functionalized low-cis polybutadiene rubber (LCBR) obtained as described above was transferred to an 800 liter batch autoclave equipped with a temperature regulator, stirring system, vacuum regulation system and condensate recovery system: the autoclave was thermostated at 25°C and placed under vacuum at a pressure of 70 mbar. As soon as the presence of liquid was confirmed in the condensate recovery system, 248.8 Kg of styrene was slowly added and at the same time the temperature of the autoclave was increased to 66°C: the solvent exchange operation was terminated when 290.9 Kg of condensate had been collected. The cyclohexane concentration in the styrene solution was less than 500 ppm: the final solution was stored in a buffer tank and the concentration of functionalized low-cis polybutadiene rubber (LCBR) in styrene at the end of the solvent exchange operation was equal to 21.5%.

[0237] An aliquot corresponding to 21.1 Kg of functionalized low-cis polybutadiene rubber (LCBR) at 21.1% in styrene was transferred to a 50 liter vessel equipped with an agitator, which was then fed with the following: 5.2 Kg of styrene, 3.7 Kg of ethylbenzene, 11.5 g of di-1,1-bis(tert-butylperoxy)cyclohexane [Trigonox22-E50 (Tx22E50)] (radical initiator), 55.6 g of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox® 1076) (antioxidant) and 16.7 g of n-dodecyl mercaptan (NDM) chain transfer agent. The solution thus obtained was fed continuously at a flow rate of 3.8 Kg / h to a 10 liter first plug flow reactor (PFR) (R1) equipped with an agitator and a temperature control system. A flow of acrylonitrile was added to the solution at a rate of 0.7 Kg / h just before entering the first plug flow reactor (PFR) (R1). The temperature profile of the reactor was increased from 113° C. to 122° C. and the stirring speed was kept constant at 80 rpm. In said first plug flow reactor (PFR) (R1), prepolymerization with grafting and phase inversion was carried out. A solution of n-dodecyl mercaptan (NDM) chain transfer agent in ethylbenzene (EB) [33.0 g of NDM in 0.967 kg of EB corresponds to a concentration of 3.3% of NDM in ethylbenzene] was continuously added (0.15 kg / h) to the mixture leaving the plug flow reactor (PFR) (R1) and fed to a second plug flow reactor (PFR) (R2) also equipped with an agitator and temperature control system, and the temperature profile of the reactor was increased from 139° C. to 150° C., while the agitation speed was kept constant at 10 rpm.

[0238] The resulting mixture was fed to a devolatilizer operating under vacuum at a temperature of 255°C to remove unreacted styrene and solvent from the copolymer to obtain the final copolymer. The reaction conditions used in this process are shown in Table 1c. The characteristics of the product obtained are shown in Table 2d.

[0239] [Table 4]

[0240]

Table 5

[0241]

Table 6

[0242]

Table 7

[0243]

Table 8-1

Table 8-2

[0244]

Table 9-1

Table 9-2

Table 9-3

[0245]

Table 10-1

Table 10-2

Table 10-3

[0246]

Table 11-1

Table 11-2

[0247] The results shown in Tables 2a to 2d are as follows:

[0248] Weight average molecular weight (M) equal to 115447 w ) and non-functionalized styrene-butadiene rubber (SBR) (Comparative Example 1) having different weight average molecular weights (M w ), i.e. 60206 g / mol in Example 2 (Comparative Example), 77561 g / mol in Example 3 (Comparative Example) and 91586 g / mol in Example 4 (Comparative Example). Comparative Examples 1 to 4 result in copolymers that can only show a part of the properties of the copolymers of interest according to the invention: in particular, the use of non-functionalized rubbers results in good gloss values ​​(i.e. values ​​of 58 to 63) and impact resistance (i.e. values ​​below 16 kJ / m 2 It is possible to obtain products which are characterized by high gloss sensitivity values ​​(i.e. values ​​greater than 1) and low stab resistance values ​​(i.e. values ​​less than 400 J*mm). - the volume diameter of the particles is too large [larger than 0.37 μm, except for Example 2 (comparative example)]; - too high a proportion of particles with a mean volume diameter of more than 0.40 μm [more than 50% except for Example 2 (comparative) and Example 3 (comparative)]; The ratio of blocked / unblocked particles is greater than 1.9, except for Example 2 (comparative), Example 3 (comparative) and Example 4 (comparative).

[0249] It should be noted that the use of functionalized low-cis polybutadiene rubber (LCBR) having functional groups makes it possible to obtain rubber particles having an average volume diameter according to the present invention. In addition, the weight average molecular weight (M w) are the same (see Tables 2b, 2c and 2d), it should also be noted that the distribution of the average volume diameter of the rubber particles is also observed to be influenced by the amount of chain transfer agent n-dodecyl mercaptan (NDM) added before the phase inversion [i.e. in the first plug flow reactor (PFR) (R1)]. In fact: - too little amount of n-dodecyl mercaptan (NDM) in the first plug flow reactor (PFR) (R1) results in small to medium volumetric diameter LCBR rubber particles [Example 5 (Comparative), Example 8 (Comparative) and Example 11 (Comparative)], resulting in a product characterized by low impact resistance and low puncture resistance values; - it is observed how, by increasing the amount of n-dodecyl mercaptan (NDM) in the first plug flow reactor (PFR) (R1), the average volume diameter of the LCBR rubber particles increases [Example 6 (inventive example), Example 9 (inventive example) and Example 12 (inventive example)], and as a result, an improvement in the mechanical properties [particularly in terms of impact resistance and puncture resistance] is observed, without observing a deterioration in the aesthetic properties [particularly in terms of gloss and gloss sensitivity]; - By further increasing the amount of n-dodecyl mercaptan (NDM) in the first plug flow reactor (PFR) (R1), it can be observed as a further increase in the average volume diameter of the LCBR rubber particles [Example 7 (Comparative), Example 10 (Comparative) and Example 13 (Comparative)], which leads to a deterioration in the mechanical properties [especially the puncture resistance and aesthetics.

[0250] The weight average molecular weight (M w ) and the weight average molecular weight (M wIt should be noted that by the combination between the amount of n-dodecyl mercaptan (NDM) used in the first plug flow reactor (PFR) (R1) used, the correct volume distribution of the rubber particles and thus the correct proportion of rubber particles having a volume diameter of more than 0.40 μm and the correct ratio of rubber particles containing and not containing blockages (particles containing blockages / particles not containing blockages), etc.

[0251] Furthermore, the ratios reported above, i.e.:

number

Claims

1. (a) a polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer; (b) dispersed therein are rubber particles obtained by a continuous bulk process from a functionalized low-cis polybutadiene rubber (LCBR): (i) the rubber particles have an average volume diameter of 0.25 μm to 0.37 μm, preferably 0.26 μm to 0.36 μm, and more preferably 0.27 μm to 0.35 μm; (ii) the volume of said rubber particles having a diameter greater than 0.40 μm is 20% to 50%, preferably 25% to 45%, more preferably 30% to 40%, based on the total volume of dispersed rubber particles; (iii) A rubber-reinforced vinyl aromatic (co)polymer, characterized in that the ratio of rubber particles containing pluggings to rubber particles not containing pluggings (particles containing pluggings / particles not containing pluggings) is 0.9 to 1.9, preferably 1.0 to 1.8, more preferably 1.2 to 1.

7.

2. The vinyl aromatic monomer has the following general formula (I): 【Chemical 1】 2. The rubber-reinforced vinyl aromatic (co)polymer according to claim 1, wherein the vinyl aromatic (co)polymer is selected from vinyl aromatic monomers having the formula: (wherein R is a hydrogen atom or a methyl group, n is 0 or an integer of 1 to 5, and Y is a halogen atom such as chlorine or bromine, or an alkyl or alkoxy group having 1 to 4 carbon atoms).

3. 3. The rubber-reinforced vinyl aromatic (co)polymer according to claim 2, wherein the vinyl aromatic monomer having general formula (I) is selected from: styrene, α-methylstyrene, methylstyrene, ethylstyrene, butylstyrene, dimethylstyrene, mono-, di-, tri-, tetra- and penta-chlorostyrene, bromo-styrene, methoxy-styrene, acetoxy-styrene, or mixtures thereof; preferably selected from styrene, α-methylstyrene.

4. The comonomer is: (meth)acrylic acid; C of (meth)acrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, butyl acrylate, etc. １ -C ４ 2. The rubber-reinforced vinyl aromatic (co)polymer according to claim 1, selected from alkyl esters; amides and nitriles of (meth)acrylic acid such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile; imides such as N-phenylmaleimide; divinylaromatic monomers such as divinylbenzene; anhydrides such as maleic anhydride; or mixtures thereof; preferably selected from acrylonitrile, methyl methacrylate.

5. In the rubber-reinforced vinyl aromatic (co)polymer, the polymer matrix comprising at least one vinyl aromatic monomer and at least one comonomer has a weight average molecular weight (M) of 145,000 g / mol or less, preferably 140,000 g / mol or less, more preferably 90,000 g / mol to 135,000 g / mol. ｗ 2. The rubber-reinforced vinyl aromatic (co)polymer of claim 1, wherein

6. 2. The rubber-reinforced vinyl aromatic (co)polymer according to claim 1, wherein in the rubber-reinforced vinyl aromatic (co)polymer, the functionalized low-cis polybutadiene rubber (LCBR) is present in an amount of 5% to 35% by weight, preferably 8% to 30% by weight, more preferably 10% to 25% by weight, based on the total weight of the rubber-reinforced vinyl aromatic (co)polymer.

7. In the rubber-reinforced vinyl aromatic (co)polymer, the rubber particles obtained from the functionalized low-cis polybutadiene rubber (LCBR) by a continuous bulk process have the following characteristics: - A weight average molecular weight (M) of 40,000 g / mol to 110,000 g / mol, preferably 50,000 g / mol to 100,000 g / mol, more preferably 55,000 g / mol to 95,000 g / mol ｗ ); A polydispersity index (PDI), i.e., a weight average molecular weight (M ｗ ) and number average molecular weight (M ｎ ) ratio (M ｗ / M ｎ ); - The content of 1,4-cis units is 10% to 70% by weight, preferably 20% to 60% by weight, more preferably 30% to 50% by weight; the content of 1,4-trans units is 20% to 80% by weight, preferably 30% to 70% by weight, more preferably 40% to 60% by weight; and the content of 1,2-vinyl units is 0% to 25% by weight, preferably 0% to 20% by weight; more preferably 5% to 15% by weight of double bond isomer components (microstructure) in the rubber chain; and a functionalized low-cis polybutadiene rubber (LCBR) having the formula:

2. The rubber-reinforced vinyl aromatic (co)polymer according to claim 1, wherein the low cis polybutadiene rubber (LCBR) is functionalized with a functional group capable of promoting controlled chain radical polymerization mediated by stable free nitroxyl radicals; and the low cis polybutadiene rubber (LCBR) has a functionality of 1 or less per rubber polymer chain, preferably 0.05 to 1, more preferably 0.2 to 0.8, and even more preferably 0.3 to 0.

7.

8. In the rubber-reinforced vinyl aromatic (co)polymer: - Weight average molecular weight (M ｗ ) is 8000 g / mol to 70000 g / mol, preferably 10000 g / mol to 60000 g / mol, more preferably 15000 g / mol to 50000 g / mol; - Polydispersity index (PDI) of the free functionalized low-cis polybutadiene rubber (LCBR), i.e., weight average molecular weight (M ｗ ) and number average molecular weight (M ｎ ) ratio (M ｗ / M ｎ ) is 1.3 or more, preferably 1.4 or more, more preferably 1.5 or more; 2. The rubber-reinforced vinyl aromatic (co)polymer according to claim 1, wherein the double bond isomer composition (microstructure) of the free functionalized low-cis polybutadiene rubber (LCBR) is as follows: the content of 1,4-cis units is 10% to 70% by weight, preferably 20% to 60% by weight, more preferably 30% to 50% by weight; the content of 1,4-trans units is 20% to 80% by weight, preferably 30% to 70% by weight, more preferably 40% to 60% by weight; and the content of 1,2-vinyl units is 0% to 25% by weight, preferably 0% to 20% by weight; more preferably 5% to 15% by weight.

9. In the rubber-reinforced vinyl aromatic (co)polymer, the weight average molecular weight (M ｗ ) (M ｗ LCBR ｌ , expressed in g / mol), the average volume diameter of the rubber particles (D ｖｍ , expressed in μm), the volume of rubber particles larger than 0.40 μm in diameter (% particles ＞０．４μｍ ), the ratio of rubber particles containing blockages to rubber particles without blockages (ratio 閉塞部位／非閉塞部位 ), and the weight average molecular weight of the polymer matrix (M ｗ ) (M ｗ SAN, expressed in g / mol) satisfies the following relationship: [Equation 1] Preferably: [Equation 2] More preferably: [Equation 3] are connected by π is equal to 3.14 and the term NSG has the following formula: [Equation 4] 2. The rubber-toughened vinyl aromatic (co)polymer of claim 1, defined according to

10. The gloss value measured at −20° is 50 or more, preferably 55 or more, and more preferably 60 or more; a gloss sensitivity of 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less; Impact resistance measured at -23°C is 12 kJ / m ２ or more, preferably 14 kJ / m ２ More preferably, 16 kJ / m ２ That's all; The rubber-reinforced vinyl aromatic (co)polymer according to any one of claims 1 to 9, characterized in that it has a puncture resistance, calculated as the product of the displacement at break (expressed in mm) and the energy at break (expressed in J), of at least 400 J*mm, preferably at least 450 J*mm, more preferably at least 500 J*mm.

11. (a) In a low boiling point solvent, the weight average molecular weight (M ｗ obtaining a functionalized low-cis polybutadiene rubber (LCBR) having a carboxyl group content of 40,000 g / mol to 110,000 g / mol, preferably 50,000 g / mol to 100,000 g / mol, more preferably 60,000 g / mol to 95,000 g / mol; (b) discontinuously exchanging the low boiling point solvent with a vinyl aromatic monomer; (c) storing a solution of the functionalized low-cis polybutadiene rubber (LCBR) in a vinyl aromatic monomer in a buffer tank according to the grade of the obtained functionalized low-cis polybutadiene rubber (LCBR); (d) delivering an aliquot of the solution of functionalized low-cis polybutadiene rubber (LCBR) in vinyl aromatic monomer stored in the buffer tank to a vessel, adding additional aliquots of vinyl aromatic monomer to achieve the desired rubber concentration in the reaction mixture, and adding at least one solvent, at least one radical polymerization initiator, at least one chain transfer agent, and additional conventional additives; (e) continuously feeding the solution obtained in step (d) into a first plug flow reactor (PFR) (R1), feeding a stream comprising at least one comonomer just before entering said first reactor (R1); (f) continuously feeding the reaction mixture leaving said first reactor (R1) into a second plug flow reactor (PFR) (R2), which is also continuously fed with a solution of at least one chain transfer agent in a solvent; (g) recovering the rubber-toughened vinyl aromatic (co)polymer from the polymerization plant; The weight average molecular weight (M ｗ ) (expressed in g / mol), the amount of chain transfer agent (expressed in ppm, i.e., the amount by weight of chain transfer agent fed to the first plug flow reactor (PFR) (R1) [step (e)]) (expressed in g / mol), the amount by weight of chain transfer agent fed to the first plug flow reactor (PFR) (R1) [step (e)] (expressed in ppm, i.e., the amount by weight of chain transfer agent fed relative to the total weight of compounds fed in the [step (e)]), and the average volume diameter (expressed in μm) of the functionalized low-cis polybutadiene rubber (LCBR) particles satisfy the following relationship: [Equation 5] Preferably [Equation 6] More preferably [Equation 7] 1. A process for preparing rubber-reinforced vinyl aromatic (co)polymers, characterized in that the process is related by:

12. - in step (d), the solvent is selected from aromatic solvents such as ethylbenzene, toluene, xylene or mixtures thereof; or aliphatic solvents such as hexane, cyclohexane or mixtures thereof; or mixtures thereof; preferably ethylbenzene; and / or - in step (d), the at least one radical initiator is added in an amount of from 0% to 0.7% by weight, preferably from 0% to 0.6% by weight, more preferably from 0.02% to 0.5% by weight, relative to the total weight of the reaction mixture; and / or in step (d), the at least one radical initiator is selected from the group consisting of 4,4'-bis-(di-iso-butyronitrile), 4,4'-bis(4-cyanopentanoic acid), 2,2'-azobis(2-amidinopropane) dihydrochloride; peroxides; hydroperoxides; percarbonates; peresters; or mixtures thereof, which have an activation temperature between 40°C and 170°C, preferably between 50°C and 150°C, more preferably between 70°C and 140°C; preferably tert-butyl-iso-propyl monoperoxycarbonate, tert-butyl 2-ethylhexyl and / or selected from peroxides such as cumyl peroxycarbonate, dicumyl peroxide, di-tert-butyl peroxide, 1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane (di-tert-butylperoxycyclohexane), tert-butyl peroxyacetate, cumyl tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, or mixtures thereof; and / or - in step (d), the at least one chain transfer agent is added in an amount of 0.01% to 1% by weight, preferably 0.1% to 0.8% by weight, more preferably 0.15% to 0.6% by weight, relative to the total weight of the reaction mixture; and / or - in step (d), the at least one chain transfer agent is selected from mercaptans such as n-octyl mercaptan, n-dodecyl mercaptan (NDM), tert-dodecyl mercaptan, mercaptoethanol or mixtures thereof; preferably n-dodecyl mercaptan (NDM); and / or A process for preparing rubber-toughened vinyl aromatic (co)polymers according to claim 11, wherein said step (d) is carried out at a temperature between 30°C and 90°C, preferably between 40°C and 80°C.

13. - in step (e), the at least one comonomer is added in an amount of from 5% to 35% by weight, preferably from 10% to 30% by weight, more preferably from 17% to 27% by weight, relative to the total weight of the reaction mixture; and / or A process for preparing rubber-toughened vinyl aromatic (co)polymers according to claim 11, wherein said step (e) is carried out at a temperature between 100°C and 130°C, preferably between 110°C and 125°C.

14. - in step (f), the at least one chain transfer agent is added in an amount of from 0.5% to 2.5% by weight, preferably from 0.7% to 2.2% by weight, more preferably from 0.9% to 2% by weight, relative to the total weight of the reaction mixture; and / or - Process for preparing rubber-toughened vinyl aromatic (co)polymers according to any one of claims 11 to 13, wherein step (f) is carried out at a temperature between 120°C and 160°C, preferably between 130°C and 155°C.

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