JP4070688B2 - Process for producing block copolymer - Google Patents

Description

  The present invention deactivates an active terminal by adding while spraying pure water to a block copolymer solution having an active lithium terminal obtained by anionic polymerization using an organolithium compound as a polymerization initiator in a hydrocarbon solvent. The present invention relates to a method for efficiently obtaining a block copolymer having a small gel content, excellent color tone and transparency, and suitable for use as a sheet / film and a heat-shrinkable film.

  A block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene is a resin having excellent transparency and impact resistance, and is therefore widely used in sheets, films, injection molded articles and the like. In producing these block copolymers, the polymerization is usually carried out in a hydrocarbon solvent inert to the catalyst, and the resulting block copolymer is uniformly dissolved or suspended in the solvent. Since it is obtained in a state, a step of separating the block copolymer and the solvent is required. As a method for separating the block copolymer and the solvent, a steam stripping method or a direct devolatilization method is generally known, but in recent years, a direct devolatilization method which is advantageous in terms of cost is often used.

  In the production method of the block copolymer using the direct devolatilization method, the vinyl aromatic hydrocarbon and the conjugated diene are polymerized by anionic polymerization in a hydrocarbon solvent, and the active terminal is deactivated by an appropriate terminator. A method of directly devolatilizing after stabilizing the catalyst residue is often used. Water is often used for deactivation of the active terminal in the block copolymer solution obtained by the anionic polymerization method. Next, as a means for neutralizing and stabilizing the catalyst residue, carbon dioxide is used as the polymer or polymer solution. The method of contacting with is common. For example, in a polymerization can containing a polymer solution having an active end, water is added to deactivate the active end, and a method of neutralizing by blowing carbon dioxide, or a polymer solution having an active end is deactivated. A method of transferring to a holding can dedicated to stabilization and neutralizing by adding pure water and blowing carbon dioxide in the can is generally performed. However, in these methods, since attention is not paid to the addition method, addition amount, etc. of water, it was not possible to stably obtain a block copolymer having a small gel content and excellent color tone and transparency. . Furthermore, in the method of recovering a polymer by deactivating active ends under specific conditions, it is necessary to combine two kinds of terminators, or the average particle size of pure water added for deactivating active ends is 15 μm or less. However, there remains a problem that mixing and high dispersion are required (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 10-324711 Japanese Examined Patent Publication No. 6-72174

  Under such circumstances, the active lithium terminal obtained by anionic polymerization of at least one vinyl aromatic hydrocarbon and at least one conjugated diene using an organolithium compound as a polymerization initiator in a hydrocarbon solvent is used. In a method for separating a block copolymer directly from the block copolymer solution using a devolatilization method, a method for stably producing a block copolymer having a low gel content and excellent color tone and transparency is required. It was.

  As a result of intensive studies on the amount and method of addition of water as a terminator for deactivating the active terminal in the block copolymer solution, the present inventors have started the block copolymer solution having an active lithium terminal. After spraying a 1.2-fold mole to 6.0-fold mole amount of pure water with respect to the number of moles of lithium of the organolithium compound as an agent, stirring and mixing to deactivate the active lithium terminal, The present inventors have found that the object can be achieved by blowing carbon dioxide into a polymer solution that is generally performed to stabilize the catalyst residue, and have completed the present invention.

  According to the present invention, the amount and method of addition of the polymerization terminator to the block copolymer solution having active ends are extremely important for the quality of the block copolymer (low gel content, good color tone and transparency). By finding this role and specifying this condition, it is possible to stably obtain a block copolymer having a small gel content in the pellet and excellent in color tone and transparency.

Hereinafter, the present invention will be described in detail.
In the present invention, it is obtained by polymerizing a vinyl aromatic hydrocarbon and a conjugated diene in a hydrocarbon solvent using an organolithium compound as an initiator, and the mass ratio of the vinyl aromatic hydrocarbon unit to the conjugated diene unit is 60 to 90. : It is preferable that it exists in the range of 40-10. When the mass ratio of the conjugated diene exceeds 40, when the sheet or film is stretched, the gel content increases, and a product excellent in color tone and transparency may not be obtained. Moreover, when the mass ratio of the conjugated diene is less than 10, the physical properties of the sheet and the film tend to be lowered.

  The number average molecular weight of the block copolymer is preferably 40,000 to 500,000. If it is less than 40,000, sufficient rigidity may not be obtained in the obtained sheet and film, and if it exceeds 500,000, workability may be deteriorated.

  The block ratio of the vinyl aromatic hydrocarbon in the block copolymer is preferably 70 to 100%. If it is less than 70%, the transparency and rigidity of the sheet and film may be lowered. [However, block ratio (%) = (W1 / W0) × 100, where W1: indicates the mass of the vinyl aromatic hydrocarbon block polymer chain in the block copolymer, and the block copolymer is subjected to ozonolysis. Calibration obtained by using standard polystyrene and styrene oligomer for molecular weight corresponding to each peak in GPC measurement of the obtained vinyl aromatic hydrocarbon polymer component (using UV spectroscopic detector with wavelength set to 254 nm as detector) It calculated | required from the line and quantified and calculated | required more than the number average molecular weight 3,000 from the peak area. W0: indicates the total mass of vinyl aromatic hydrocarbon units in the block copolymer, and is the mass of all vinyl aromatic hydrocarbons used in the polymerization. ]

  When there is a random copolymer part of vinyl aromatic hydrocarbon and conjugated diene in the polymer block mainly composed of vinyl aromatic or polymer block mainly composed of conjugated diene, the copolymerized vinyl aromatic is It may be evenly distributed in the polymer block or may be a tapered chain in which the ratio of vinyl aromatic hydrocarbon and conjugated diene continuously changes. Further, the copolymer portion may coexist with a plurality of portions where vinyl aromatic hydrocarbons are uniformly distributed and / or portions where they are distributed in a tapered shape.

  Examples of the block copolymer used in the present invention include, for example, Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 43-17879, Japanese Patent Publication No. 48-2423, Japanese Patent Publication No. 49-36957, Japanese Patent Publication No. 60-46009. And JP-B-7-13089, JP-B-7-13092, JP-A-9-143222, JP-A-10-17611, and the like.

The basic skeleton of such a block copolymer is, for example, the general formula (AB) n
(AB) n-A
(BA) n-B
(In the formula, A represents a polymer block mainly composed of vinyl aromatic hydrocarbon, and B represents a polymer block mainly composed of conjugated diene such as butadiene and isoprene, or a copolymer block composed of vinyl aromatic hydrocarbon and conjugated diene. Represents a polymer block, and n is an integer of 1 or more, generally an integer of 1 to 5.)

Or [(AB) n-] mX
[(BA) n-] mX
[(AB) n-A-] mX
[(BA) n-B-] mX
(In the formula, A and B are as defined above, and X is the start of carboxylic acid ester such as silicon tetrachloride, tin tetrachloride, polyhalogenated hydrocarbon, phenyl benzoate, or polyfunctional organolithium compound) Represents a residue of the agent, and m and n are integers of 1 or more, generally 1 to 5).

  In the present invention, examples of the vinyl aromatic compound that forms the block copolymer include styrene, о- or p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, Examples thereof include vinyl naphthalene and vinyl anthracene, and styrene is particularly preferably used. The vinyl aromatic compound may be used alone or in combination of two or more.

  The conjugated diene used in the present invention is a diolefin having a pair of conjugated double bonds, such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1. 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc., with 1,3-butadiene, isoprene and the like being particularly common. These may be used alone or in combination of two or more.

Examples of the hydrocarbon solvent include cyclohexane, aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, and octane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, methylcyclohexane, and ethylcyclohexane, or benzene. Aromatic hydrocarbons such as toluene, ethylbenzene and xylene can be used, and among these, cyclohexane is preferred. These may be used alone or in combination of two or more.
Generally the quantity of these hydrocarbon solvents is 50-1500 mass parts with respect to 100 mass parts of polymers.

  The organic lithium compound used as the polymerization initiator is an organic monolithium compound, organic dilithium compound, or organic polylithium compound in which one or more lithium atoms are bonded in the molecule. Specific examples thereof include, for example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium, and the like. Is mentioned. These may be used alone or in combination of two or more.

  In the present invention, polar compounds or random compounds are used for the purpose of adjusting the polymerization rate, changing the microstructure of the polymerized conjugated diene moiety (ratio of cis, trans, vinyl), and adjusting the reaction ratio of vinyl aromatic hydrocarbon and conjugated diene. An agent can be used. Examples of polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium and sodium And alkoxides.

  In the present invention, the polymerization temperature for producing the block copolymer is generally -10 to 160 ° C. The time required for polymerization varies depending on the variety, conditions and the like, but is generally 1 to 12 hours. The atmosphere of the polymerization system is preferably replaced with an inert gas such as nitrogen gas. The polymerization pressure can be set within a range of pressure sufficient to maintain the monomer and solvent in the liquid layer within the above polymerization temperature range. Further, care must be taken not to mix impurities (for example, water, oxygen, carbon dioxide gas, etc.) that deactivate the polymerization initiator and the living polymer in the polymerization system.

Next, post treatment of the obtained polymer solution will be described.
In the present invention, it is essential that the terminator used for deactivating the active terminal is pure water. And the pure water which is a terminator for deactivating the active terminal in the block copolymer solution is 1.2 times mole to 6.0 times mole with respect to the number of moles of lithium of the organolithium compound which is the initiator. It is characterized by adding while spraying in a quantity.

If the number of moles of the terminator added is less than 1.2 times the number of moles of lithium of the organolithium compound as the initiator, the time required for complete deactivation may be increased, or the active terminal There is a case where the entire amount of can not be deactivated. In addition, when the terminator is more than 6.0 times the molar amount of the organolithium compound as the initiator, the resulting block copolymer is often mixed with bumps.
In the next operation, the block copolymer is usually neutralized and stabilized with carbon dioxide gas in order to stabilize the deactivated catalyst residue. In particular, when pure water is used as a terminator for deactivation of the active terminal, when the amount of pure water used exceeds 6.0 times the molar amount of the organolithium compound, the block copolymer solution contains As a result, a large amount of undissolved water droplets are present, and the catalyst residue stabilized with carbon dioxide gas tends to aggregate in the undissolved water droplets, which may increase the amount of block copolymer obtained. In addition, this agglomerate also causes clogging of a polymer liquid filter or the like in the middle process, which also hinders stable operation.
When the active terminal is deactivated, if pure water is added while sprayed, the surface area becomes larger than when it is added all at once, so that the time required for complete deactivation can be shortened. Furthermore, since agglomerates of catalyst residues are hardly formed after the neutralization operation, it is preferable in terms of suppression of blur and stable operation.

  As the polymerization termination measure, the polymerization and addition of the terminator to the polymer solution may be performed in the polymerization vessel where the polymerization has been performed, or the polymerization is performed in the polymerization vessel, and only the subsequent polymerization termination measure is performed exclusively. It may be transferred to a tank (hereinafter referred to as a hold tank) for processing.

In order to stop the polymerization, it is necessary to mix the stopper and the block copolymer solution. Although there is no restriction | limiting in particular in the stirring power in this case, 0.1-1 kW / m < ³ > is preferable. If it is less than 0.1 kW / m ³ , the time required for deactivation may be extremely long. If it exceeds 1 kW / m ³ , a large amount of equipment is required, which is not preferable in terms of cost. The stirring blade is not particularly limited, but it must be capable of obtaining a uniform mixed solution when operated under the above conditions. Examples include Max blend blades, paddle blades, pitched paddle blades, propeller blades, flat turbine blades, pitched turbine blades, anchor blades, and the like, and those composed of Max blend blades are preferred.

  Next, a method for neutralizing and stabilizing the catalyst residue after the polymerization stoppage will be described. As a method of neutralizing and stabilizing the catalyst residue in the block copolymer solution, carbonic acid gas is blown into the block copolymer solution after mixing the active ends and mixed to neutralize the catalyst residue and stabilize. Make it.

  Carbon dioxide gas is intermittently brought into contact with the polymer in the polymerization can or hold tank in which the polymerization is stopped. In addition, after stopping the polymerization, in the step of continuously transferring the block copolymer solution to the next step (for example, the step of devolatilizing the solvent), carbon dioxide gas is continuously supplied in the middle of the piping provided for the transfer. The block copolymer solution and carbon dioxide gas are mixed by blowing a static mixer or a known stirring and mixing device having a similar stirring ability. Alternatively, a mixing tank may be provided, and carbon dioxide gas may be continuously blown into the mixing tank for stirring and mixing. The residence time of the block copolymer solution here is at least 3 minutes or more, preferably 10 minutes or more, and more preferably 1 hour or more.

  At the time of bringing the block copolymer solution into contact with carbon dioxide, it is important that the block copolymer solution contains a large amount of solvent, and the solvent is at least 30 parts by mass with respect to at least 100 parts by mass of the block copolymer solution. It must be 95 parts by weight or less, preferably 50 parts by weight or more and 80 parts by weight or less. Further, the amount of carbon dioxide to be supplied must be equal to or more than the number of moles of catalyst residue in the block copolymer solution.

  The addition amount is adjusted so that the pH of the neutralized block copolymer solution is in the range of 6.5 to 8.3. If the pH exceeds 8.3, the stabilizer added in any step after the completion of the polymerization reaction is denatured, so that the color tone of the polymer deteriorates and the thermal stability decreases, which is not preferable. Moreover, if the pH is less than 6.5, there is a possibility of equipment corrosion, which is not preferable. Here, the pH of the block copolymer solution refers to 50 g of the solution and 50 g of pure water (having a pH of 6.5 ± 0.5) placed in a separatory funnel, mixed well, and then allowed to stand and separate. It is the value which measured the pH of the layer. The pH can be measured with a general pH meter.

  After neutralizing and stabilizing the catalyst residue in the block copolymer solution with carbon dioxide, the block copolymer solution is sent to a devolatilization step for separating the polymer and the solvent. Although there is no limitation in particular as a devolatilization process, A flash distillation apparatus, an extruder with a vent, etc., and what combined these are mentioned.

  When the solvent is removed using a direct devolatilization method, a stabilizer can be used in any step after completion of the polymerization reaction in order to prevent oxidative degradation and thermal degradation of the block copolymer. As a stabilizer used for preventing oxidative degradation and thermal degradation of the block copolymer, for example, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4, 6-di-tert-pentylphenyl acrylate, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl-4-methylphenyl acrylate, octadecyl-3- (3,5- Phenolic antioxidants such as di-tert-butyl-4-hydroxyphenyl) propionate, 2,6-di-tert-butyl-4-methylphenol, 2,2-methylenebis (4,6-di-tert-butyl) Phenyl) octyl phosphite, trisnonylphenyl phosphite, bis (2,6-di-tert-butyl-4-methyl) (Phenyl) pentaerythritol-di-phosphite, etc. These stabilizers may be added to the block copolymer solution as they are, but once dissolved in a hydrocarbon solvent, they are added. These stabilizers are generally desirably used in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the block copolymer.

The manufacturing method of the block copolymer used in the Example below is shown. Further, the present invention is not limited to the following examples.
[Block copolymer (A)]
The polymerization vessel was placed in a nitrogen gas atmosphere, 70 g of n-butyllithium was added to 268 kg of cyclohexane, 16 kg of styrene was added, and polymerization was performed at 45 ° C. for 10 minutes, and then 2 kg of butadiene was added and polymerization was performed for 50 minutes. Thereafter, 7 kg of butadiene was added followed by 33 kg of styrene, and polymerization was carried out at 85 ° C. for 60 minutes. Further, 2 kg of butadiene was added and polymerized for 20 minutes. Thereafter, 7 kg of butadiene and then 33 kg of styrene were added and polymerized at 80 ° C. for 60 minutes to obtain a block copolymer solution having a styrene content of 82% by mass (polymer concentration 27% by mass).

[Block copolymer (B)]
The polymerization vessel is placed in a nitrogen gas atmosphere, 180 g of n-butyllithium is added to 257 kg of cyclohexane, then 22 kg of styrene is added and polymerized at 55 ° C. for 20 minutes, and then 45 kg of butadiene and then 33 kg of styrene are added. Polymerization was performed at 120 ° C. for 110 minutes to obtain a block copolymer solution having a styrene content of 55% by mass (polymer concentration 28% by mass).

[Block copolymer (C)]
The polymerization can was placed in a nitrogen gas atmosphere, 70 g of n-butyllithium was added to 223 kg of cyclohexane, 34 kg of styrene was added, and polymerization was performed at 65 ° C. for 20 minutes, and then 12 kg of butadiene was added and polymerization was performed for 50 minutes. Thereafter, 3 kg of butadiene and then 51 kg of styrene were added and polymerized at 100 ° C. for 80 minutes to obtain a block copolymer solution having a styrene content of 85% by mass (polymer concentration 31% by mass).

  100 g of pure water was added to the polymerization can containing the solution of the block copolymer (A) having an active lithium terminal obtained by the above method while spraying. The amount of water added corresponds to a 5.1-fold molar amount relative to the number of moles of the organolithium compound used. The polymerization can was stirred with a Max Blend blade, stirred for 30 minutes after addition of pure water, and then 300 g of carbon dioxide gas was supplied without stopping stirring. Stirring continued even after the carbon dioxide gas was supplied, and after 30 minutes from the carbon dioxide gas supply, the block copolymer solution was sampled and the pH of the solution was measured to be 7.2. As a stabilizer, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate was added to this mixture as a block copolymer (A) 100. 0.2 mass part was added with respect to the mass part, and it stirred for 20 minutes as it was, and mixed uniformly. The pure water spray nozzle used at this time is a two-fluid spray nozzle manufactured by Spraying System Far East Company, which has a capacity of 0.13 L / min.

  After treating with carbon dioxide, it is heated to a polymer temperature of 180 ° C by a preheater provided before being transferred to the devolatilizing extruder, concentrated to a polymer concentration of 61% with a concentrator by flash evaporation, and biaxial devolatilization with a vent. Pelletized by an extruder. The discharged polymer temperature at that time was 242 ° C. Regarding the color tone measurement of the pellet, the b value of the pellet was measured using a NDJ-300A measuring instrument manufactured by Nippon Denshoku Industries Co., Ltd. The larger the b value, the larger the apparent yellowness.

Subsequently, the obtained pellets were extruded at 210 ° C. to produce a sheet having a thickness of 0.2 mm. Thereafter, the obtained sheet was subjected to lateral uniaxial stretching 4 times at 90 ° C. using a biaxial stretching apparatus manufactured by Toyo Seiki Seisakusho Co., Ltd., thereby producing a film having a thickness of 50 μm and evaluating its transparency. Regarding the evaluation method, measurement was performed in accordance with ASTM-D1003.
Further, 50 g of pellets were dissolved in 200 g of toluene, and suction filtered with a filter paper having a diameter of 70 mm (thickness: 0.2 mm, supplemental particle size: 6 μm, collection efficiency: 65%), and then supplemented on the filter paper with violet 36. The gel content in the pellet was dyed and classified into the following grades by visual judgment.
1: 0 large gels, 0 medium gels, 2 or less small gels 2: 0 large gels, 2 or less medium gels, 3-10 small gels 3: 0 large gels, 3-5 medium gels Hereinafter, 3 to 8 small gels, or 0 large gels, 2 or less medium gels, 11 to 20 small gels 4: 1 to 2 large gels, or 6 to 10 medium gels, or small gels 21 to 50 Individual 5: 3 or more large gels, 11 or more medium gels, or 51 or more small gels Here, the large gel has a diameter of 0.5 mm or more, the medium gel has a diameter of 0.2 mm or more and less than 0.5 mm, the small gel is Those with a diameter of less than 0.2 mm.
These results are shown in Table 1.

  Using a block copolymer (B) solution having an active lithium terminal, 300 g of pure water added after completion of the polymerization (corresponding to 5.9 times the amount of moles of the organic lithium compound used), carbon dioxide gas Except that the amount was 750 g, the active end was deactivated and the carbon dioxide gas was treated in the same manner as in Example 1. At that time, the pH of the block copolymer solution was 6.8. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 1.

  Using a block copolymer (C) solution having an active lithium terminal, the pure water added after completion of the polymerization is 36 g (corresponding to 1.8 times the molar amount of the number of moles of the organic lithium compound used). Except for the above, in the same manner as in Example 1, the active terminal was deactivated and treated with carbon dioxide gas. At that time, the pH of the block copolymer solution was 7.9. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 1.

  Using a block copolymer (A) solution having an active lithium terminal, the pure water added after the completion of the polymerization is 25 g (corresponding to 1.3 times the molar amount with respect to the number of moles of the organic lithium compound used). Except for the above, in the same manner as in Example 1, the active terminal was deactivated and treated with carbon dioxide gas. The resulting block copolymer solution had a pH of 7.5. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 1.

The active terminal was deactivated and treated with carbon dioxide gas in the same manner as in Example 1 except that the stirring power during the deactivation operation was 0.2 kW / m ³ . The time required for complete deactivation was 80 minutes, and the pH of the block copolymer solution after neutralization was 8.2. Thereafter, in the same manner as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 1.

  Except for changing the amount of carbon dioxide to be added to 150 g, in the same manner as in Example 1, deactivation of the active terminal and carbon dioxide treatment were performed. At that time, the pH of the block copolymer solution was 8.5. Thereafter, in the same manner as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 1.

[Comparative Example 1]
Using the block copolymer (A) solution having an active lithium terminal, the active terminal was deactivated and treated with carbon dioxide gas in the same manner as in Example 1 except that pure water was added all at once after the completion of the polymerization. The obtained block copolymer solution had a pH of 8.0. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 2.

[Comparative Example 2]
Deactivation of the active terminal, carbon dioxide gas, in the same manner as in Comparative Example 1 except that the block copolymer (A) solution having an active lithium terminal was used and the stirring power during the deactivation operation was changed to 0.8 kW / m ^3. Processed. The resulting block copolymer solution had a pH of 8.1. Thereafter, in the same manner as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 2.

[Comparative Example 3]
Using a block copolymer (A) solution having an active lithium terminal, 16 g of pure water added while spraying after completion of the polymerization (corresponding to 0.8 times the molar amount of the number of moles of the organic lithium compound used) In the same manner as in Example 1 except that the active terminal was deactivated and carbon dioxide gas treatment was performed. The pH of the obtained block copolymer solution was 8.3. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 2.

[Comparative Example 4]
Using the block copolymer (A) solution having an active lithium terminal, 393 g of pure water added while spraying after completion of the polymerization (corresponding to 20.0 times mole amount with respect to the number of moles of the organic lithium compound used) In the same manner as in Example 1 except that the active terminal was deactivated and carbon dioxide gas treatment was performed. The resulting block copolymer solution had a pH of 7.5. Thereafter, as in Example 1, solvent removal, pelletization, and film formation were performed, and transparency and gel amount were evaluated. The results are shown in Table 2.

According to the present invention, the block copolymer obtained according to the present invention is a sheet, a film because the block copolymer obtained with the present invention can stably obtain a block copolymer having a low gel content and excellent color tone and transparency. It can be fully satisfied with the quality required for such applications (low buzz, excellent color tone and transparency), and can be used for sheets, films, injection-molded products of various shapes, etc. that make use of the characteristics.

Claims (6)

A block copolymer solution having an active lithium terminal, obtained by anionic polymerization of at least one vinyl aromatic hydrocarbon and at least one conjugated diene using an organolithium compound as a polymerization initiator in a hydrocarbon solvent Is added while spraying pure water in an amount of 1.2-fold to 6.0-fold mole with respect to the number of moles of lithium of the organolithium compound as an initiator, and stirred to mix to deactivate the active lithium terminal. The pellet which consists of a block copolymer obtained by the manufacturing method characterized by the above-mentioned. In the block copolymer, the mass ratio of the vinyl aromatic hydrocarbon unit and the conjugated diene unit is 60 to 90:40 to 10, and the number average molecular weight of the block copolymer is 40,000 to 500,000, 2. The pellet comprising the block copolymer obtained by the production method according to claim 1, wherein the block ratio of the vinyl aromatic hydrocarbon polymer contained in the block copolymer is 70 to 100%. . The pellet made of the block copolymer obtained by the production method according to claim 1, wherein the stirring power during stirring and mixing is 0.1 to 1 kW / m ³ . Any sheet pellet comprising a stretching process to comprising a single term block copolymer according to claims 1-3. Any pellets obtained by stretching a film made of a block copolymer of one of claims 1 to 3. The film according to claim 5, wherein the film is a heat-shrinkable film.