JPS6141927B2 - - Google Patents

Description

[Detailed description of the invention]

A block polymer containing ABA of α-methylstyrene and butadiene (where A is a block of α-methylstyrene and B is a block of butadiene) is disclosed in British Patent No. 1444680 and “the
Journal of Applied Polymer Science”
Vol. 22, 2907-2913 (1978).
α-Methylstyrene has a relatively low sealing temperature of about 61° C. (the temperature at which the depolymerization rate and the polymerization rate are the same). In general, alpha-methylstyrene polymerizes slowly and, because of its low sealing temperature, operations must be carried out at relatively low temperatures. Copolymers of styrene and α-methylstyrene have shown promise in US Pat. Nos. 4,431,777 and 4,427,837, but are extremely difficult to produce economically. The reactivity ratio between styrene and α-methylstyrene is such that an economically unreasonable amount of α-methylstyrene must be used to obtain a 1:1 copolymer. Anionic polymerizations require the use of relatively large amounts of solvent to yield desirable block copolymers. In the production of such copolymers, therefore, solids contents of only 10-15% are conveniently obtained. Producing in situ polymer blends of random isopropenyl aromatic-vinyl aromatic copolymers (with and without diene blocks), particularly of random styrene/α-methylstyrene copolymers and block polymers. It would be extremely desirable if an improved production method using liquid solution polymerization became practical. Furthermore, it would be extremely desirable if an improved method of anionic polymerization capable of producing a polymer solution having a solids content of 20% by weight or more could be put to practical use. According to the invention, these advantages are achieved in a process for producing thermoplastic aromatic polymer blends consisting essentially of the following steps: (a) Eq. where R is hydrogen or a lower alkyl group having up to 4 carbon atoms; at least one vinyl aromatic monomer of the formula Here, R is hydrogen or a lower alkyl group having 4 or less carbon atoms; dissolves in isopropenyl aromatic monomer to form a solution; adds organolithium initiator to initiate polymerization to form vinyl aromatic in isopropenyl monomer. (b) polymerizing at least a major portion of a group monomer, butadiene, isoprene, or a mixture thereof to form a first solution of the polymer dissolved in isopropenyl aromatic monomer; then stopping the polymerization; Dissolving the vinyl aromatic monomer, butadiene, isoprene, or a mixture thereof; initiating the polymerization to create a solution of the blended polymers in the isopropenyl aromatic monomer; stopping the polymerization again; (c) increasing as desired; Repeat step (b) to make additional in-situ polymer blends: In the present invention, after anionic copolymerization of isopropenyl aromatic monomers, vinyl aromatic monomers, and optionally a diene, 1. Utilizing the functions of the remaining unreacted isopropenyl aromatic monomer as a solvent and a monomer, one of the above monomers other than the isopropenyl aromatic monomer is additionally added to the system and copolymerized.
This process is repeated more than once, and different types of polymer blends can be produced depending on the type, amount, number of times, etc. of additional monomers. In the present invention, since steps (a) and after (b) are separated, the product can generally be regarded as a polymer blend of the copolymer from step (a) and the copolymer from step (b). Vinyl aromatic monomers suitable for the practice of this invention have the formula Here, R is a compound selected from the group consisting of hydrogen and a lower alkyl group having 4 or less carbon atoms. Such monomers include styrene, para-methylstyrene, meta-ethylstyrene and para-tertiary-butylstyrene. The isopropenyl aromatic monomer used in the practice of this invention has the formula Here, R is as defined above; Examples include α-methylstyrene and para-methyl-α-methylstyrene. Isopropenyl aromatic monomers are used both as active monomers and as solvents. However, it may contain from 0 to 50% by weight, based on the weight of the isopropenyl aromatic monomer, of inert hydrocarbon solvents such as cyclohexane, hexane, heptane, benzene and toluene. The term "random" as used in the present invention is not used in the sense that the two monomers in the copolymer are present in a one-to-one alternation that corresponds strictly to random statistics. This term refers to the absence of long block-like structures of polymerized vinyl aromatic monomers or polymerized isopropenyl aromatic monomers. The resulting block copolymer can be elastomeric or resinous depending on the ratio of components selected. Triblock polymers made with low proportions of diene, such as 5 to 40 weight percent polybutane diene, are generally resinous, transparent, and particularly suitable for packaging applications. High proportion of polydiene blocks, for example 50-98%, preferably 5-90% by weight
Polydienes of the present invention provide desirable elastomers or thermoplastic elastomers with improved green strength.
Polymers containing about 40-50% by weight diene can be considered soft plastics. The molecular weight of the block copolymers of the invention, determined by gel permeation chromatography, can vary from 5,000 to 800,000. Particularly desirable polymers for most applications have a molecular weight range of 10,000 to 500,000. Preferably, polymer block B is an elastomeric polymer block of an unsaturated diene such as butadiene, isoprene or mixtures thereof, and polymer block A is a random copolymer of α-methylstyrene and styrene and α-methylstyrene and para-methylstyrene. It is a plastic polymer block like this. The block copolymers of the invention may be of linear AB or ABA configuration or of configuration with side chains such as AB(BA) _o . In the production of linear polymers such as ABA, difunctional lithium initiators are used, and in the production of side-chained or radial polymers with AB(BA) _o , multifunctional lithium polymerization initiators are used. Multifunctional lithium-containing initiators and their use in the polymerization of olefinically unsaturated hydrocarbon monomers are described in U.S. Pat.
4172190 and 4205016. A highly desirable lithium initiator is 2
It can be produced by adding 2 moles of an organolithium compound such as secondary butyllithium to 1 mole of a compound having 1,1-diphenylethylene groups. The method of the present invention is applied to random copolymers or random copolymers in the presence of an organolithium polymerization initiator.
When used to produce random copolymers of isopropenyl aromatic monomers and vinyl aromatic monomers, either as polydienes or graded diene polymer blocks, the reaction is self-terminating and the rate of self-termination increases with increasing temperature. . Although this termination mechanism is not fully understood, it is often not necessary to add an active hydrogen compound to terminate the polymerization before proceeding to the next polymerization step. However, in order to inactivate the polymer,
Partial or full amounts of terminators may be used. It is preferred to use 60 to 90% of the theoretical amount of terminating agent required for termination. The method of the invention can be used in various embodiments. In the simplest embodiment, a polymer with a desired molecular weight distribution can be produced. When monomers are fed in the same manner and polymerization is carried out continuously with organolithium initiation, both narrow and wide molecular weight distributions can be easily obtained by using an appropriate amount of the organolithium initiator. By varying the monomer feed, A, AB and AB can be produced without the need for conventional mechanical blending.
(BA) Blends of any combination of _o are easily obtained. Several methods can be used to make AB block copolymers using initiators such as sec-butyllithium or n-butyllithium. Tapered AB block copolymers can be made by mixing alpha-methylstyrene, butadiene, and styrene monomers and adding an initiator to form a tapered AB polymer. Alternatively, alpha-methylstyrene and diene are mixed, an initiator is added, the diene is polymerized, and styrene monomer is subsequently added to the reaction mixture to form the styrene-
A polymer having a polybutadiene block attached to an α-methylstyrene copolymer block is prepared. A similar block copolymer can be prepared by mixing α-methylstyrene with styrene and adding the diene immediately after the styrene-α-methylstyrene copolymerization is complete to form a polydiene block and an α-methylstyrene-styrene copolymer block in the AB polymer. It can be created by occurring. ABA polymers are readily obtained using the method of the present invention using difunctional organolithium initiators. For example, a tapered ABA α-methylstyrene-styrene-diene polymer can be obtained by mixing α-methylstyrene, styrene, and butadiene, adding an initiator, and polymerizing. Alternatively, mix α-methylstyrene and butadiene, add an initiator, and when the polymerization of butadiene is completed, add a styrenic monomer such as styrene to create an ABA α-methylstyrene-styrene-terminated block and a polybutane diene central block. Polymers with ABA configuration can also be made using monofunctional initiators such as sec-butyllithium or n-butyllithium. For example, by mixing α-methylstyrene and styrene monomer, adding an initiator, adding a diene monomer when the copolymerization is complete, and adding a coupling agent to the reaction mixture when the diene polymerization is complete, ABA
It is possible to create polymers with different configurations. Another route to ABA polymers is to mix the aromatic monomers with a monofunctional initiator, add the diene once the copolymerization of the aromatic monomers is complete, and add additional vinyl aromatic monomers once the polymerization of the diene monomers is complete. It is added to the reaction mixture, resulting in an ABA polymer with a polydiene central block and aromatic end blocks. Alternatively, if copolymerization of a vinyl aromatic monomer-isopropenyl aromatic monomer mixture is started and a diene monomer is added before the copolymerization is completed, a polymer with an ABA configuration can be obtained. So-called radial, star or multi-armed polymers, ie polymers with many branches, are preferably prepared using polyfunctional initiators and using the general methods described above. Depending on the length of monomer addition, either a tapered copolymer or a polydiene block is obtained. Another route to radial block copolymers is to create a living polymer in the AB configuration and then use a multifunctional coupling agent such as silicon tetrachloride or divinylbenzene. By using the method of the invention, for example, styrene and initiator can be added alternately to the reaction mixture to
To enable copolymerization with methylstyrene, these additions are made when the polymerization has clearly stopped and become inert. The heat of polymerization is desirably removed by conventional means, such as conduction, use of a jacket reactor, or evaporation of a solvent boiling at the desired polymerization temperature. The polymerizations of this invention are generally carried out at temperatures between about 20° and 160°C, most preferably between 40° and 120°C. Because of the different reactivities of vinyl aromatic monomers and isopropenyl aromatic monomers, isopropenyl aromatic monomers are generally present in higher proportions in the polymerization solution than in the resulting polymer. The invention also makes it possible to increase the solids content in the polymerization mixture to a level limited only by the viscosity of the mixture which can be easily processed in the equipment. The present invention will be illustrated in the following examples. Example 1 168 g of α-methylstyrene was placed in a flask and 0.109 mmol of sec-butyllithium dissolved in cyclohexane was added at room temperature to inactivate oxygen and other undesirable impurities. The flask and contents were heated in a water bath to 57-75°C for approximately 15 minutes, and 9.2 mmol of styrene and 0.147 mmol of sec-butyllithium dissolved in cyclohexane were added. After about 10 minutes, the contents of the flask changed from colorless to orange to red to orange. After heating for an additional 15 minutes to ensure self-termination of the reaction chain, 8.8 ml of styrene monomer and 0.136 mmol of sec-butyllithium dissolved in cyclohexane were added for a second polymerization. After each reaction chain self-termination, additional feeds of styrene monomer and secondary butyllithium were made four times under the conditions shown in the table below.

[Table] * Time used for self-stop Styrene monomer and secondary butyl lithium 6
2 ml of isopropyl alcohol 20 minutes after the first addition
was added to stop the polymer. A 1.823g sample of the polymer solution was heated in vacuo at 170°C for 30 minutes to yield 0.805g (44.2% by weight) of residual polymer. The remaining reaction mixture was diluted with methanol to precipitate the polymer. NMR analysis showed that the polymer had 51% by weight α-methylstyrene and 49% by weight styrene. The weight average molecular weight measured by gel permeation chromatography is 143000, and the ratio of weight average molecular weight to number average molecular weight is
It was 1.43. Example 2 A triblock copolymer was prepared as follows: 9.542 mmol of sec-butyllithium dissolved in 17.1 ml of cyclohexane and 4.776 mmol of 1,3-di(1-phenylethenyl)benzene dissolved in 40 ml of toluene. A difunctional lithium initiator was created by reacting at room temperature for about 20 hours. The resulting solution contained 0.0817 mmol of dilithium initiator per ml of solution. 1400 ml of α-methylstyrene was placed in a jacketed reactor with a hollow auger stirrer and 0.67 mmol of sec-butyllithium dissolved in cyclohexane at room temperature was added to inactivate the oxygen and other active hydrogen impurities present. Ta. 54.2 g of 1,3-butadiene and 63.5 g of styrene were added and heated to about 55°C. 26 ml (2.12 mmol) of difunctional lithium initiator solution was added and the jacket temperature was maintained at approximately 55°C.
After about 90 minutes, the color of the reactor contents changed from yellow to red and the temperature of the reaction mixture rose to about 70°C. The jacket temperature was held at about 55°C for about 110 minutes after addition of the difunctional lithium initiator and then raised to 75°C for an additional 30 minutes to ensure self-termination of the reaction chain.
Approximately 130 g of the reaction mixture was removed for analysis. The polymer recovered from this solution (solid content: 13.8% by weight) is referred to as "Polymer A." Cool the contents of the reactor to approximately 25°C and add butadiene.
46.4 g and 54.5 g of styrene were added and then heated to about 55°C. 21 ml of difunctional initiator solution (containing 1.72 mmol of initiator) was added. After 110 minutes, the jacket temperature was increased to 65°C. Approximately 135 minutes after the second addition of styrene and butadiene, the reaction mixture was raised to approximately 77°C and 30 minutes later the reaction was stopped by adding 3 ml of isopropyl alcohol. The reaction mixture contained 24.8% solids by weight (Polymer B). From the reaction mixture to which a small amount of ionol (2,6-ditert-butyl-4-methylphenol) was added as a stabilizer, polymers A and B were prepared by precipitation in methanol.
A blend of As measured by gel permeation chromatography, polymers A and B are each
They had molecular weights of 114,000 and 106,000. Polymers A and B were analyzed by NMR. The weight composition was as follows: Polymer A α-methylstyrene 32.2% Styrene 35.7% Butadiene 32.1% Polymer B α-methylstyrene 32.3% Styrene 34.9% Butadiene 32.8% The properties of Polymer B measured on compression molded pieces were as follows: The results were as follows: Tensile yield strength 22.4 MPa Ultimate elongation 45% Tensile modulus 1120 MPa Izod impact strength 46 J/m Nottibikatsu softening point 116°C Example 3 The method of Example 2 was followed except that isoprene was used instead of butadiene. Compliant, tapered styrene-α-methylstyrene isoprene styrene-α-
Created a methylstyrene triblock polymer. Polymer C was prepared using the following amounts in the first polymerization step: α-methylstyrene 127 g styrene 76 g isoprene 49 g dilithium initiator 2.84 mmol Self-termination was ensured at 70° C. for about 50 minutes. The amounts of reactants in the second stage of polymerization to make Polymer D were as follows. Polymer solution from C 1274 g Styrene 63.5 g Isoprene 40.8 g Dilithium initiator 2.03 mmol Upon quenching with 1 ml isopropyl alcohol, the reaction mixture contained approximately 24.1% solids by weight. The composition, molecular weight, and properties of the triblock copolymer obtained were as follows. Composition (weight) Polymer C: α-methylstyrene 36.7% Styrene 38.6 Isoprene 24.7% Polymer D: α-methylstyrene 37.1% Styrene 38.0% Isoprene 24.9% Polymer C by gel permeation chromatography
The molecular weight of is 117000, and the molecular weight of polymer D is
It was 95,000. The materials of Polymer D were as follows: Tensile strength at break 15.4 MPa Ultimate elongation 0.9% Tensile modulus 1760 MPa Izod impact strength 20 J/m Nottibikatsu softening point 114°C Example 4 Butadiene in a 1:1 weight ratio instead of butadiene A tapered styrene-α-methylstyrene-butadiene-isoprene styrene-α-methylstyrene triblock copolymer was prepared by following the procedure of Example 2, except that a mixture of and isoprene was used. Polymer E was prepared using the following ingredients: α-methylstyrene 1271 g Styrene 76 g Isoprene 31 g Butadiene 31 g Dilithium initiator 2.90 mmol Self-termination was ensured at 70° C. for 30 minutes. Polymer F was prepared using the following ingredients: 1309 g of polymer solution from E 63.5 g of styrene 25.9 g of isoprene 25.8 g of butadiene 2.71 mmol of dilithium initiator When stopped with 1 ml of isopropyl alcohol, the reaction mixture contained 25.9% solids by weight. there was. Each of the triblock copolymers had a molecular weight of 110,000 as determined by gel permeation chromatography. The weight percent composition of polymers E and F is: α-methylstyrene 33.7%; styrene 36.5%; isoprene
14.9% and butadiene 14.9%. The physical properties of Polymer E were as follows. Tensile yield strength 25.0MPa Ultimate elongation 27.2% Tensile modulus 1020MPa Izot impact strength 28J/m Notch softening point 116℃ Example 5 Tapered styrene-α was obtained by repeatedly adding the method of Example 2 except for the following conditions. -Methylstyrene-butadiene-isoprene-styrene-α-methylstyrene triblock copolymer and styrene-α-methylstyrene copolymer were created:
Polymer G is a triblock copolymer made by replacing butadiene with a 1:1 weight mixture of butadiene and isoprene. Polymer H is a mixture of Polymer G and styrene-α-methylstyrene copolymer. However, no diene is used in the second stage of polymerization. The following reactants were used: For Polymer G: α-methylstyrene 1271 g Styrene 33.6 g Isoprene 22.5 g Butadiene 23.2 g Dilithium initiator 2.20 mmol Self-termination was ensured at 70° C. for about 40 minutes. The following reagents were used for Polymer H: Polymer solution from G 1256 g Styrene 59 g Tirus sec-butyllithium 1.19 mmol Polymer G has a molecular weight of 106,000 by gel permeation chromatography and contains 34.1% α-methylene and styrene. 27.9%, isoprene 18.7%, butadiene 19.3
It had a weight composition of %. Polymer H has a molecular weight of 97,000 determined by gel permeation chromatography, and has a molecular weight of 42.4 α-methylstyrene.
%, styrene 39.1%, isoprene 9.1%, and butadiene 9.4%. The physical properties of Polymer H were measured on a compression molded product and were as follows: Tensile yield strength 40.1 MPa Ultimate elongation 3.6% Tensile modulus 2300 MPa Izot impact strength 26 J/m Notch softening point 132°C Example 6 As follows. A tapered styrene-α-methylstyrene butadiene styrene-α-methylstyrene triblock copolymer was prepared. 61.10 kg of α-methylstyrene purified through an activated alumina bed was placed in a 30 gallon reactor and 20
The α-methylstyrene was deoxygenated by applying a vacuum at °C to release nitrogen. The remaining impurity is 1.4318N second
It was inactivated by adding 44 ml (36 mmol) of a butyl lithium solution. Then 1.65 Kg of oxygen-free styrene without inhibitor and 6.62 Kg of 1,3-butadiene purified through a bed of DOWEX® MSC-1K ⁺ type ion exchange beads were added, followed by the addition of activated alumina. A 19 Kg portion of feed was removed from the reactor. 10 ml of purified tetrahydrofuran was added to 1.8 kg of this solution, and 0.1663N secondary butyllithium dissolved in cyclohexane was added until color appeared. Measurements showed that the amount of impurities in the remaining feed, consisting of 59.43 Kg of α-methylstyrene, 6.44 Kg of butadiene and 161 Kg of styrene, corresponded to 5 mmol of difunctional lithium initiator. Reactor contents to 38℃
and 5 mmol of the difunctional lithium initiator prepared as in Example 2 were added to inactivate impurities. After about 5 minutes, 91 mmol (0.0919 mmol per solution) of difunctional lithium initiating solvent was added to initiate polymerization. Within 2 hours the temperature of the reaction mixture was 87
The temperature rose to ℃. After 2.5 hours, add 9.5 ml to 20 ml of toluene.
A solution of isopropyl alcohol was added to terminate the polymer chain. Approximately 1.2 Kg of the reaction mixture was removed for analysis. The polymer recovered from this solution (solid content 15.5% by weight) is referred to as "polymer". The contents of the reactor were cooled to 20 °C and the butadiene
Added 6.05Kg and 1.55Kg of styrene. Reactor at 47℃
and 83 mmol (0.0899 mmol/g solution) of difunctional lithium initiator were added. Within 70 minutes the temperature of the reaction mixture rose to 95°C. After 100 minutes, 30 ml of isopropyl alcohol was added. The reaction mixture contained 26.8% solids by weight (Polymer J). Polymers I and J were recovered by precipitation in methanol from a portion (approximately 100 g) of the reaction mixture to which a small amount of ionol was added as a stabilizer. Polymers I and J according to gel permeation chromatography
had molecular weights of 125,000 and 132,000, respectively. According to NMR, both polymers I and J are α
-It had a weight composition of 23.9% methylstyrene, 15.0% styrene, and 61.1% butadiene. The physical properties of Polymers I and J for compression molded pieces were as follows: Polymer I: Tensile strength at break 21.3 MPa Elongation at break 730% Polymer J: Tensile strength at break 22.3 MPa Elongation at break 780% Example 7 Monomer and A tapered styrene-α-methylstyrene-butadiene-α-methylstyrene triblock copolymer was prepared by the method of Example 6, except that the initiator was added once more. Polymer K was prepared using the following ingredients: α-methylstyrene 58.28 Kg Styrene 3.00 Kg Butadiene 2.61 Kg Dilithium initiator 128 mmol After the reaction was completed, a solution of 12.6 ml of isopropyl alcohol in 20 ml of toluene was added to separate the polymer chains. It stopped. This solution contained 14.25% solids by weight. Polymer L was prepared using the following ingredients: Polymer solution from K 64.33 Kg Styrene 2.77 Kg Butadiene 2.37 Kg Dilithium initiator 121 mmol After the reaction was complete, a solution of 12.6 ml of isopropyl alcohol in 20 ml of toluene was added. The added polymer chains were terminated. This solution contained 24.63% solids by weight. Polymer M was prepared using the following components: Polymer solution from L 68.94 Kg Styrene 2.33 Kg Butadiene 1.99 Kg Dilithium initiator 103 mmol When the polymerization was stopped with a solution of 25 ml toluene and 43 ml acetic acid, the reaction mixture was 32.44 kg. % solids by weight. When the resulting triblock copolymer was analyzed by NMR, its composition (weight) was as follows: Polymer K: α-methylstyrene 33.9% Styrene 34.3% Butadiene 31.8% Polymer L: α-methylstyrene 33.1% Styrene 35.2% Butadiene 31.7% Polymer M: α-methylstyrene 33.4% Styrene 35.4% Butadiene 31.2% The molecular weights measured by gel permeation chromatography were 100,000 for Polymer K, 95,000 for Polymer L, and 95,000 for Polymer M. Example 8 A polymer blend was prepared consisting of two different compositions of styrene-α-methylstyrene butadiene styrene-α-methylstyrene triblock copolymer and styrene-α-methylstyrene random copolymer. The procedure of Example 6 was followed by repeating the addition of styrene monomer and initiator three more times. The ingredients used to make Polymers N, O, P, Q, and R were as follows: For Polymer N: α-methylstyrene 58.99Kg Styrene 1.78Kg Butadiene 1.52Kg Dilithium initiator 108 mmol After the reaction was completed, The solution was kept at 62°C for 15 hours to ensure self-termination of the reaction chain. For Polymer O: Polymer solution from N 63.12 Kg Styrene 0.68 Kg Butadiene 4.27 Kg Dilithium initiator 86 mmol After completion of the reaction, the solution was kept at 65° C. for 13 hours to ensure self-termination of the reaction chain. This solution is
It contained 18.46% solids by weight. For Polymer P: Polymer solution from O 68.74 Kg Styrene 2.81 Kg Sec-Butyllithium 40 mmol After completion of the reaction, the solution was held at 75° C. for 40 minutes to ensure self-termination of the reaction chain. For Polymer Q: Polymer solution from P 71.55 Kg Styrene 2.30 Kg Sec-Butyllithium 36 mmol After completion of the reaction, the solution was held at 75° C. for 40 minutes to ensure self-termination of the reaction chain. This solution is
It contained 32.48% solids by weight. For Polymer R: Polymer solution from Q 73.85 Kg Styrene 1.59 Kg Secondary butyl lithium 37 mmol After the reaction was completed, 50 ml of isopropyl alcohol was added. This solution contained 37.13% solids by weight. Produced polymer N, O, P, measured by NMR
The compositions of Q and R were as follows:

[Table] The properties of Polymer R measured on the injection molded piece were as follows: Tensile yield strength 36.5MPa Ultimate elongation 16% Tensile modulus 2480MPa Izod impact strength 25J/m Notsubikatsu softening point 122℃

Claims (1)

[Claims] 1 (a) Formula where R is hydrogen or a lower alkyl group having up to 4 carbon atoms; optionally with at least one diene selected from butadiene and isoprene; Here, R is hydrogen or a lower alkyl group having 4 or less carbon atoms; Prepare a freshly dissolved solution in an isopropenyl aromatic monomer represented by (b) polymerizing at least a major portion of the vinyl aromatic monomer or diene to form a first solution of the polymer dissolved in the isopropenyl aromatic monomer; then stopping the polymerization; (b) adding additional vinyl to the first polymer solution; dissolving at least one of the aromatic monomers or the diene;
A method for producing a polymer blend comprising at least one step of initiating polymerization to form a solution of blend polymers in isopropenyl aromatic monomer; and stopping polymerization again. 2 (b) Claim 1 in which the process is repeated two or more times
The method described in section. 3. The method of claim 1, wherein the polymer blend comprises a random copolymer of vinyl aromatic monomers and isopropenyl aromatic monomers. 4. The method of claim 1, wherein the polymer blend comprises a block copolymer having 5 to 90% by weight of polydiene moieties. 5 Polymer blend contains 5 to 40% by weight vinyl aromatic-isopropenyl aromatic random copolymer
5. A method according to claim 4, consisting essentially of a block copolymer having polydiene moieties of: 6 Polydiene part is block copolymer 40-90
5. A method according to claim 4, wherein the amount is % by weight. 7. The method according to claim 1, wherein the isopropenyl aromatic monomer is α-methylstyrene and the vinyl aromatic monomer is styrene. 8. The method according to claim 1, wherein the vinyl aromatic monomer is para-methylstyrene. 9. The method according to claim 1, wherein the diene is butane diene. 10. The method of claim 1, wherein the in-situ prepared polymer blend is a thermoplastic elastomer. 11. The method of claim 1, wherein the resulting polymer solution contains at least 20% by weight of polymer formed by in situ anionically initiated polymerization.