JPH0360843B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a block copolymer obtained by polymerizing a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator, or a hydrogenated product thereof. When obtaining lithium using the steam stripping method, the remaining amount of lithium is small by combining specific processing steps,
The present invention relates to a method for obtaining a block copolymer or a hydrogenated product thereof having excellent transparency and devitrification resistance. [Prior Art] A block copolymer composed of a conjugated diene and a vinyl aromatic hydrocarbon is transparent when the vinyl aromatic hydrocarbon content is relatively small and can be used as a vulcanized natural rubber or vulcanized natural rubber without vulcanization. It has the same elasticity as synthetic rubber at room temperature and the same processability as thermoplastic resin at high temperatures, so it is widely used in the fields of footwear, plastic modification, asphalt, adhesives, etc. In addition, when the vinyl aromatic hydrocarbon content is relatively high, a thermoplastic resin that is transparent and has excellent impact resistance can be obtained, so its use has increased in recent years, mainly in the food packaging container field, and at the same time its applications have also increased. It is becoming more diverse. When producing these copolymers, polymerization is usually carried out in a hydrocarbon solvent that is inert to the catalyst, and the produced copolymers are either uniformly dissolved in the solvent or in a suspended state. Because you can get
A step of separating the copolymer and the solvent and recovering the copolymer is required. There are various methods for separating a copolymer and a solvent, one of which is a steam method in which a polymer solution is injected into hot water, the solvent is distilled together with steam, and the polymer is precipitated in the form of crumbs. A stripping method is known. In such a method, various proposals have been made to use an appropriate dispersant to improve dispersion of the polymerization solution in hot water, prevent agglomeration of the polymer, and form crumbs of appropriate size. Examples of dispersants include polyether block copolymers (Japanese Patent Application Laid-open No. 89494/1983)
(Japanese Patent Application Laid-open No. 1983-37987), polycarboxylic acid salts (Japanese Patent Application Laid-open No. 49-53991, JP-A No. 1973-
141693), polyvinyl alcohol (JP-A-Sho
50-90693), cellulose derivatives (Japanese Patent Application Laid-open No. 1983)
-90693), phosphoric acid ester (JP-A-47-
Publication No. 22687). [Problems to be Solved by the Invention] However, although it is possible to obtain a crumb-like polymer of an appropriate size by steam stripping in the presence of a dispersant as described above, it is difficult to obtain transparency and loss resistance. Unable to obtain one with good transparency,
Improvements are desired. [Means for Solving Problems] Under the current circumstances, the present inventors have developed a method for steam stripping block copolymers or their hydrogenated products to obtain good crumb and at the same time improve transparency and devitrification resistance. As a result of studying methods to obtain excellent block copolymers or their hydrogenated products, we found that
The inventors have discovered that by combining specific treatment steps, the objective can be achieved and a block copolymer or its hydrogenated product with a small residual amount of lithium can be obtained, and the present invention has been completed. That is, the present invention provides a block having a vinyl aromatic hydrocarbon content of 5 to 95% by weight, which is obtained by polymerizing a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator. When obtaining a block copolymer or its hydrogenated product by steam stripping the solvent from a solution of the copolymer or hydrogenated product, the following (1) to (5)
The remaining amount of lithium can be
The present invention relates to a method for obtaining a block copolymer or a hydrogenated product thereof having a concentration of 40 ppm or less. (1) A step of adding at least one reaction terminator selected from (a) water, (b) alcohol, (c) inorganic acids, and (d) organic acids to a solution of the block copolymer or its hydrogenated product. (2) A step of adding a stabilizer to the solution of the block copolymer or its hydrogenated product. (3) A solution of the block copolymer or its hydrogenated product having a polymer concentration of 10 to 60% by weight is mixed with the following phosphate ester (e) and/or phosphate ester salt (f) from 0.1 to 0.1%.
In the presence of 1000 ppm (weight ratio of the stripping zone to water), the boiling point of the hydrocarbon solvent or the azeotropic temperature if the solvent and water are azeotropic,
A process of stripping at a temperature below 120°C to obtain a slurry in which crumb-like polymers are dispersed in water. (e) one selected from the group consisting of polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkylaryl ether phosphate, and polyoxyalkylene alkenyl aryl ether phosphate; or Two or more phosphoric acid esters (f) Alkali of polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkylaryl ether phosphate, and polyoxyalkylene alkenyl aryl ether phosphate One or more phosphate ester salts selected from the group consisting of metal salts and ammonium salts. (4) The moisture-containing block copolymer or its hydrogenated crumb obtained above is dehydrated to reduce the moisture content to 1.
Process to make ~30% by weight. (5) Drying the block copolymer or its hydrogenated product obtained above to reduce the water content to less than 1% by weight. The present invention will be explained in detail below. The solution of the block copolymer or its hydrogenated product used in the steam stripping method of the present invention is obtained by polymerizing a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator. . The vinyl aromatic hydrocarbon content of the block copolymer and hydrogenated product is from 5 to 95% by weight, preferably from 10 to 90% by weight. Methods for producing block copolymers include, for example, Japanese Patent Publication No. 36-19286, Japanese Patent Publication No. 43-17979, Japanese Patent Publication No. 46-32415, Japanese Patent Publication No. 49-36957, and Japanese Patent Publication No. 48-2423. , Special Publication No. 48-4106, Special Publication No. 56-28925, Special Publication No. 51-49567
Publication No. 59-166518, Japanese Patent Application Laid-open No. 166518-
Examples include the method described in Publication No. 186577. By these methods, block copolymers can be produced with the following general formulas: (A-B) _o , A(-B-A) _o , B(-A-B) _o [In the above formula, A represents a vinyl aromatic hydrocarbon. B is a polymer block mainly composed of a conjugated diene. A block and B
Boundaries with blocks do not necessarily need to be clearly distinguished. Further, n is an integer of 1 or more. ] Or the general formula, [(B-A) _o ] _n+1 −−−1X, [(A−B) _o ] _n+1 −−−X, [(B−A) _o B] _n+1 − --X, [(A-B) _o A] _n+1 ---X [In the above formula, A and B are the same as above, and
represents, for example, the residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, polyhalogenated hydrocarbon, carboxylic acid ester, or polyvinyl compound, or the residue of an initiator such as a polyfunctional organolithium compound. m and n are integers of 1 or more. ] It is obtained as a block copolymer represented by:
In the above formula, the polymer block mainly composed of vinyl aromatic hydrocarbons refers to
It refers to a copolymer block of vinyl aromatic hydrocarbon and conjugated diene containing 50% by weight or more and/or a vinyl aromatic hydrocarbon homopolymer block containing 50% by weight or more. A copolymer block of a conjugated diene and a vinyl aromatic hydrocarbon containing an amount exceeding % by weight and/or
Or a conjugated diene homopolymer block. The vinyl aromatic hydrocarbons in the copolymer block may be uniformly distributed or tapered. Further, the copolymer portion may include a plurality of portions in which vinyl aromatic hydrocarbons are uniformly distributed and/or a plurality of portions in which vinyl aromatic hydrocarbons are distributed in a tapered manner. The block copolymer used in the present invention may be any mixture of block copolymers represented by the above general formula. The block copolymer thus obtained exhibits properties as a thermoplastic elastomer when the vinyl aromatic hydrocarbon content is 60% by weight or less, preferably 55% by weight or less, and the vinyl aromatic hydrocarbon When the content exceeds 60% by weight, preferably 65% by weight or more, it exhibits properties as a thermoplastic resin. Vinyl aromatic hydrocarbons used in the method of the present invention include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3
Examples include -dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene, with styrene being particularly common. These may be used not only alone, but also as a mixture 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), 2,3-dimethyl-1,
3-butadiene, 1,3-pentadiene, 1,3
-hexadiene, etc., and particularly common ones include 1,3-butadiene and isoprene. These may be used not only alone, but also as a mixture of two or more. Hydrocarbon solvents include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, isooctane, cyclopentane,
Alicyclic hydrocarbons such as methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, or aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene can be used. These may be used not only alone, but also as a mixture of two or more. Organolithium compounds are organic monolithium compounds in which one or more lithium atoms are bonded in the molecule, such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium,
Examples include tert-butyl lithium, hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium. These may be used not only alone, but also as a mixture of two or more. In the present invention, polar compounds and Randomizing agents can be used. Examples of polar compounds and randomizing agents include ethers, amines, thioethers, phosphoramides, alkylbenzene sulfonates, potassium or sodium alkoxides, and the like. Examples of suitable ethers are dimethyl ether, diethyl ether, diphenyl ether and tetrahydrofuran, diethylene glycol dimethyl ether, diethyl glycol dibutyl ether. As the amines, in addition to tertiary amines such as trimethylamine, triethylamine, and tetramethylethylenediamine, cyclic tertiary amines and the like can also be used. Phosphines and phosphoramides include triphenylphosphine and hexamethylphosphoramide. Randomizing agents include potassium or sodium alkylbenzene sulfonate, potassium or sodium butoxide, and the like. The polymerization temperature for producing the polymer in the method of the present invention is generally -10°C to 150°C, preferably
The temperature is between 40℃ and 120℃. The time required for polymerization varies depending on the conditions, but is usually within 48 hours.
A particularly preferred time period is 0.5 to 10 hours. Further, it is desirable to replace the atmosphere of the polymerization system with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited as long as it is within a pressure range sufficient to maintain the monomer and solvent in a liquid phase within the above polymerization temperature range. Furthermore, there are impurities in the polymerization system that can inactivate the catalyst and living polymer.
For example, care must be taken to avoid contamination with water, oxygen, carbon dioxide, etc. The weight average molecular weight of the polymer thus obtained is generally 5,000 to 5,000,000, preferably 10,000 to 5,000,000.
1000000. The amount of hydrocarbon in the polymer solution is generally 50 parts by weight to 100 parts by weight of the polymer.
2000 parts by weight. Depending on the nature of the polymer, the polymer may be insoluble in the hydrocarbon solvent and may be obtained in a suspended state; however, in the present invention, these will also be referred to as a polymer solution. The block copolymer used in the present invention may be a block copolymer in which a polar group-containing atomic group is bonded to at least one polymer chain terminal of the block copolymer. The creep resistance of the adhesive composition can be improved by bonding a polar group-containing atomic group to the end of the polymer chain. Here, the polar group-containing atomic groups include nitrogen, oxygen, silicon, phosphorus,
An atomic group containing at least one atom selected from sulfur and tin. Specifically, carboxyl group, carbonyl group, thiocarbonyl group, acid halide group, acid anhydride group, carboxylic acid group, thiocarboxylic acid group, aldehyde group, thioaldehyde group, carboxylic acid ester group, amide group, sulfonic acid group. base,
Sulfonic acid ester group, phosphoric acid group, phosphoric acid ester group, amino group, imino group, nitrile group, pyridine group, quinoline group, epoxy group, thioepoxy group, sulfide group, isocyanate group, isothioneanate group, silicon halide group , alkoxy silicon group, tin halide group, alkyltin group,
Examples include atomic groups containing at least one polar group selected from phenyltin groups and the like. More specifically, the terminal-modified block copolymer described in Japanese Patent Application No. 60-224806 can be used. The hydrogenated block copolymer used in the present invention can be obtained by hydrogenating the block copolymer described above. Catalysts used in hydrogenation reactions include (1) supported heterogeneous catalysts in which metals such as Ni, Pt, Pd, and Ru are supported on supports such as carbon, silica, alumina, and diatomaceous earth; ) Uniform catalysts such as so-called Ziegler type catalysts using organic acid salts such as Ni, Co, Fe, Cr, etc. or acetylatonate salts and reducing agents such as organic Al, or so-called organic complex catalysts such as organometallic compounds such as Ru, Rh etc. catalyst is known. Specific methods are as described in Japanese Patent Publication No. 42-8704 and Special Publication No. 43
Hydrogenated products are obtained by hydrogenation in an inert solvent in the presence of a hydrogenation catalyst by the method described in JP-A-6636, JP-A-59-133203, and JP-A-60-220147. can be obtained, and the hydrogenated block copolymer used in the present invention can be synthesized. At this time, the hydrogenation rate of aliphatic double bonds based on the conjugated diene compound in the block copolymer can be controlled to any value by adjusting the reaction temperature, reaction time, hydrogen supply amount, catalyst amount, etc. In particular, when obtaining a hydrogenated product with excellent weather resistance and heat aging resistance, it is recommended that the hydrogenation rate of the aliphatic double bond based on the conjugated diene compound be 80% or more, preferably 90% or more. Ru. In this case, the aromatic double bond based on the vinyl aromatic compound copolymerized into the polymer block A mainly composed of a vinyl aromatic compound and, if necessary, the polymer block B mainly composed of a conjugated diene compound. Although there is no particular restriction on the addition rate, it is preferable that the hydrogenation rate is 20% or less. The amount of unhydrogenated aliphatic double bonds contained in the hydrogenated block copolymer can be easily determined using an infrared spectrometer, nuclear magnetic resonance apparatus, or the like. The first step of the present invention is to add (a) water, (b) alcohol,
This is a step of adding at least one reaction terminator selected from (c) inorganic acids and (d) organic acids. If a reaction terminator is not added in this step, the amount of lithium remaining in the final polymer will be large, making it impossible to obtain a polymer with excellent transparency and devitrification resistance. As the alcohol, in addition to lower alcohols such as methanol, ethanol, and propanol, higher alcohols having 6 to ₁₈ carbon atoms and polyhydric alcohols (ethylene glycol, propylene glycol, glycerin, etc.) can be used. Inorganic acids used in the present invention include acids formed by bonding acid groups containing nonmetals such as chlorine, sulfur, nitrogen, and phosphorus with hydrogen, such as hydrochloric acid, sulfuric acid, nitric acid, boric acid, phosphoric acid, and carbonic acid. can be given. The organic acid used in the present invention is an organic compound having acidity in a broad sense, and includes compounds such as carboxylic acid, sulfonic acid, sulfinic acid, and phenol, but is preferably an organic compound containing a carboxyl group. Preferably. (1) Fatty acid having 8 or more carbon atoms (2) Rosin acid (3) Oxycarboxylic acid (4) Aromatic carboxylic acid Particularly preferred organic acids are the fatty acids in (1), specific examples of which are octylic acid, capric acid, Examples include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, behenic acid, castor hydrogenated fatty acid, tallow fatty acid, or mixtures thereof. The amount of water and alcohol to be added is at least 1 mol, preferably 1.5 mol to 1000 mol, based on the lithium atom of the organolithium compound used as an initiator.
More preferably, it is 2.0 mol to 500 mol. The amount of inorganic acid and organic acid added is 0.05 to 10 mol, preferably 0.2 to 5 mol. When the amount of the inorganic acid and organic acid added is less than the equivalent molar amount, it is preferable to use them together with water. If the amount of the reaction terminator added is less than the above range, a product with excellent transparency, devitrification resistance and color tone cannot be obtained, whereas if it exceeds the above range, the devitrification resistance is poor, which is not preferable. A particularly suitable reaction terminator in the present invention is at least one selected from water, inorganic acids, and fatty acids. Next, the second step of the present invention is a step of adding a stabilizer to the solution of the above block copolymer or its hydrogenated product. Adding stabilizers at this stage is
This is effective in preventing oxidative deterioration and thermal deterioration of the polymer when the solvent is removed in the next step. Even if these are added directly to the polymer solution,
Alternatively, it may be added after being dissolved in a hydrogen oxide solvent. The stabilizer may be any of the known stabilizers conventionally used, and various known antioxidants such as phenol, organic phosphate, organic phosphite, amine, and sulfur antioxidants are used. Stabilizers are generally added to 100 parts by weight of polymer.
It is used in a range of 0.001 to 10 parts by weight. Next, in the third step of the present invention, the concentration of the polymer is reduced to 10
A solution of the block copolymer or its hydrogenated product adjusted to ~60% by weight, preferably 15 to 50% by weight, more preferably 20 to 40% by weight is mixed with phosphate ester (e).
and/or phosphate ester salt (f) 0.1-1000ppm,
Preferably 1 to 500 ppm, more preferably 3 to 500 ppm
In the presence of 300 ppm (weight ratio of the stripping zone to water), above the boiling point of the hydrocarbon solvent or the azeotropic temperature if the solvent and water are azeotropic, 120°C
The following temperature range, preferably 10 °C or more higher than the boiling point or azeotropic temperature of the solvent and 110 °C or less,
More preferably, the temperature is 15°C or more higher than the above temperature, and 100°C.
This is a process of stripping at the following temperature range to obtain a slurry in which crumb-like polymer is dispersed in water. If the concentration of the polymer is less than 10% by weight, the solvent removal efficiency is poor due to the large amount of solvent relative to the polymer, and if it exceeds 60% by weight, it is not possible to obtain small crumb particles, and the lithium removal efficiency is also poor. Undesirable because it is bad. If the amount of phosphate ester and/or phosphate ester salt added is less than 0.1 ppm, crumb particles with small particle sizes cannot be obtained, and the amount of polymer adhering to the walls of the solvent removal tank, stirring blades, etc. become more,
On the other hand, if it exceeds 1,000 ppm, foaming during steam stripping becomes so intense that stripping becomes virtually impossible, which is not preferable. If the temperature during steam stripping is below the boiling point of the solvent or below the azeotropic temperature of the solvent and water, the removal of the solvent will be poor and the amount of solvent remaining in the crumb will increase. Moreover, if the temperature during steam stripping exceeds 120°C, it is not preferable because crumb particles with a small size cannot be obtained. The phosphoric acid ester (e) used in the present invention has the general formula Polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkylaryl ether phosphate and polyoxyalkylene alkenyl aryl ether phosphate having the structure: Here, A and B can be freely and independently selected from the groups described below. That is, A
and B are hydrogen, a polyoxyalkylene alkyl ether group, a polyoxyalkylene alkenyl ether group, a polyoxyalkylene alkylaryl ether group, and a polyoxyalkylene alkenyl aryl group represented by R ₃ -O-(R ₄ -O) _-n A group selected from the group consisting of: Here, R ₁ - and R ₃ - are hydrogen, a group selected from the group consisting of an alkyl group, an alkenyl group, an alkylaryl group, and an alkenylaryl group. Alkyl groups are straight and branched hydrocarbon chains having from 1 to 20 carbon atoms, including methyl, ethyl, propyl, straight and branched butyl, octyl, dodecyl and Examples include tridecyl group. Alkenyl groups, like alkyl groups, are unsaturated hydrocarbons having from 2 to 20 carbon atoms. Allyl and oleyl groups are representative alkenyl groups, but other alkenyl groups may also be used. The alkylaryl group is a group containing the above-mentioned alkyl group and aryl group, and nonylphenol group and dodecylphenol group are representative alkylaryl groups, but other alkylaryl groups can also be used. The alkenylaryl group is a group containing the above-mentioned alkenyl group and aryl group, and the oleylphenol group is a group representative of the alkenylaryl group, but other alkenylaryl groups can also be used. R ₁ − and R ₃ − are independently selected and may be the same or different. R ₂ - and R ₄ - are alkylene groups of a polyoxyalkylene group, and are groups selected from straight chain or branched chain hydrocarbons having 2 to 4 carbon atoms. The alkylene group includes ethylene, propylene, and straight-chain and branched butylene groups. R ₂ − and R ₄ − are independently selected and may be the same or different. (-R ₂ -O)- _o and (-R ₄ -O
)-n _{, n} and m indicate the number of oxyalkylenes added. n and m are generally integers of 1 to 100, preferably 2 to 60. The phosphoric acid ester salt (f) used in the present invention has the general formula or From alkali metal salts and ammonium salts of polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkenyl ether phosphates, polyoxyalkylene alkylaryl ether phosphates and polyoxyalkylene alkenyl aryl ether phosphates having the structure selected from the group consisting of R ₁ − and R ₃ − are alkyl groups, alkenyl groups,
It represents an alkylaryl group and an alkenylaryl group, and these groups are the same as R ₁ - and R ₃ - described above. R ₂ − and R ₄ − represent an alkyl group of an oxyalkylene group, and these groups are similar to the above-mentioned R ₂ −
and R ₄ −. Me represents an alkali metal and a non-metal ammonium group; lithium, sodium, and potassium are representative alkali metals, but other alkali metals and ammonium may be used. Particularly preferred phosphoric esters and phosphoric ester salts in the present invention include R ₁ and R ₃ dodecyl groups,
It is selected from tridecyl group, nonylphenol group, and dodecylphenol group, and n and m are in the range of 2 to 60. Also, Me is lithium, sodium,
It is selected from potassium. In the present invention, in addition to the phosphoric acid ester and/or the phosphoric acid ester, Li, Na, K, Mg,
Water-soluble salts of metals such as Ca, Al, Zn, etc. can also be used as crumb dispersion aids. These water-soluble metal salts are generally used in a range of 0.1 to 1000 ppm based on the water in the stripping zone. In the present invention, the phosphate ester and/or phosphate ester salt may be added to the water in the stripping zone, or may be added to the polymer solution at the same time as the stabilizer in the second step, or after the stabilizer is added. It may be added to the coalescence solution. The polymer concentration of the polymer solution used in the third step of the present invention does not need to be particularly adjusted as long as the polymer concentration after the step of producing the polymer or the second step is within the range specified by the present invention. If the concentration is less than 10% by weight, the polymer solution is introduced into a concentrator selected from a single or multi-stage flash tank type, a stirred tank, a thin film evaporator, a wet wall tower, etc. to reduce the concentration to 10% by weight. weight%
On the other hand, if the concentration exceeds 60% by weight, it is necessary to dilute with a solvent to reduce the concentration to 60% by weight or less. The polymer solution used in the third step of the present invention contains water per 100 parts by weight of the polymer in order to obtain crumbs with good particle size uniformity.
It is also possible to premix 30 to 3000 parts by weight, preferably 50 to 2000 parts by weight, and more preferably 100 to 1000 parts by weight, and then introduce the mixture into the solvent removal tank. As the water to be mixed in advance, a part of the water from the stripping zone used in the third step may be recycled. The concentration of the crumb-like polymer dispersed in water is generally 0.1 to 20% by weight, preferably 0.5 to 15% by weight, and more preferably 1 to 10% by weight (ratio to water in the stripping zone), and within this range. If so, it is possible to obtain crumbs having a good particle size without causing any trouble in operation. Next, in the fourth step of the present invention, the moisture-containing block copolymer or its hydrogenated crumb obtained above is dehydrated to reduce the moisture content to 1 to 30% by weight, preferably 2 to 20% by weight. , more preferably 2 to 10% by weight. Here, dehydrating the crumb containing water means dehydrating it with a compressed water squeezer such as a roll, a Banbury type dehydrator, or a screw extruder type squeezer. In the present invention, a multi-screw extruder type squeeze dehydrator such as a single-screw or twin-screw extruder is preferred in terms of dewatering efficiency and workability. In the fourth step, it is preferable to reduce the water content in the crumb to less than 1% by weight because the dehydration treatment time becomes too long and the polymer gels or shatters due to the shearing force of the water squeezer. do not have. Furthermore, if the water content exceeds 30% by weight, the residual amount of lithium will increase, resulting in poor transparency and devitrification resistance. In addition, in the present invention, the slurry crumb obtained in the third step is drained in advance to a water content of 35 to 60% by weight using a rotary screen, vibrating screen, centrifugal dehydrator, etc., and then introduced into a compression water squeezer. It is preferable to do so. Next, in the fifth step of the present invention, the block copolymer or its hydrogenated product obtained above is dried to reduce the water content to less than 1% by weight, preferably 0.5% by weight or less, and more preferably 0.1% by weight. The process is as follows.
Here, drying refers to reducing the water content to less than 1% by weight using at least one type of dryer such as a screw extruder type dryer, a kneader type dryer, an expander dryer, and a hot air dryer. A particularly suitable dryer is a multi-screw bent extruder type dryer, such as a single or twin screw, with L/D (screw length/diameter)
10 to 40 can be used. If the water content in the fifth step is 1% by weight or more, it is not preferable because the polymer may foam during molding or cause appearance defects such as silver. In the fifth step, the polymer can be obtained in the form of foamed crumbs, granules or powder, or in the form of strands or pellets. In the present invention, the fourth step and the fifth step can also be carried out in an apparatus in which a dehydrator and a dryer are integrated. A suitable device of this type has at least one slit for dewatering, preferably two or more slits.
It has 4 vents, at least one vent part for deaeration,
Preferably, a vent extruder with two or more screws having two to four vent extruders is used. A vent extruder with such a structure preferably has an L/D value of about 15 to 50, and the meshing structure of the screws can be either meshing or non-meshing, and the direction of rotation can be in the same direction or in different directions. good. The screw rotation speed, cylinder superheating temperature, and vent pressure of such a vented extruder are selected taking into account extrusion capacity, polymer properties (clay and thermal stability), product quality, etc. Generally screw rotation speed 20 to 500
revolutions/min, preferably 30 to 400 revolutions/min, cylinder temperature 100 to 300°C, preferably 130 to 260°C, and vent pressure selected from the range of atmospheric pressure to 10 mmHg absolute pressure, preferably 500 to 50 mmHg absolute pressure. Ru. After the above-mentioned first to fifth steps, the final polymer has a residual lithium content of 40 ppm.
or less, preferably 30 ppm or less, more preferably
Must be less than 20ppm. If the residual amount of lithium exceeds 40 ppm, transparency and resistance to devitrification deteriorate, which is not preferable. The remaining amount of lithium in the polymer can be measured by atomic absorption spectrometry using an atomic absorption spectrophotometer. In the present invention, metal components such as lithium can also be removed by performing deashing treatment after the first step, the second step and/or the third step, or before and after these steps. In the method of the present invention, various additives can be added to the polymer depending on the purpose. for example,
Softeners such as oil, plasticizers, antistatic agents, lubricants,
Ultraviolet absorbers, flame retardants, pigments, inorganic fillers, organic and inorganic fibers, reinforcing agents such as carbon black, and other thermoplastic resins can be used as additives. Note that these additives can be added in any step after the first step. [Effects of the Invention] The present invention provides a method for efficiently obtaining a block copolymer or its hydrogenated product from a solution of the block copolymer or its hydrogenated product by a steel stripping method. The resulting polymer has excellent transparency and devitrification resistance, so by taking advantage of these characteristics, it can be used to manufacture sheets, films, injection molded products of various shapes,
In addition to being used as a wide variety of molded products such as blow molded products, pressure molded products, and vacuum molded products, it can also be used as a modification material for various thermoplastic resins, as a material for footwear, as a material for pressure-sensitive adhesives and adhesives, etc.
It can be used as a modification material for asphalt, a material for electric wires and cables, a material for vulcanized rubber, a modification material for vulcanized rubber, and a material for home appliances, automobile parts, industrial parts, household goods, toys, etc. In particular, the polymer obtained by the method of the present invention has excellent devitrification resistance, so it can be used in a humid atmosphere or in fields where it comes into contact with water, such as food containers, food packaging materials, packaging materials for food containers, It can be effectively used for toys, medical supplies, etc. [Example] The present invention will be described in more detail with reference to Examples below. The block copolymers used in the examples were produced as follows. [Block copolymer (A)] In a nitrogen gas atmosphere, 0.08 parts by weight of n-butyllithium was added to a cyclohexane solution containing 30 parts by weight of styrene and 0.3 parts by weight of tetrahydrofuran, and after polymerization at 70°C for 1 hour, further A cyclohexane solution containing 20 parts by weight of 1,3-butadiene and 50 parts by weight of styrene was added and polymerized at 70°C for 2 hours.
The obtained polymer had a styrene content of 80% by weight.
Block copolymer with B-A structure (polymer concentration 25
weight%). [Block copolymer (B)] In a nitrogen gas atmosphere, 0.15 parts by weight of n-butyllithium was added to a cyclohexane solution containing 75 parts by weight of styrene, and after polymerization at 70°C for 1 hour,
A cyclohexane solution containing 25 parts by weight of 1,3-butadiene was added and polymerized at 70°C for 2 hours. Thereafter, 5 parts by weight of epoxidized soybean oil was added to obtain a radial structure block copolymer (polymer concentration 22% by weight) with a styrene content of 75% by weight. [Block copolymer (C)] In a nitrogen gas atmosphere, 0.11 parts by weight of n-butyllithium was added to an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 20 parts by weight of styrene, and the mixture was heated at 70°C for 2 hours. After polymerization for a period of time, an n-
A hexane solution was added and polymerization was carried out at 70°C for 2 hours. The obtained polymer had a styrene content of 40% by weight.
It was a block copolymer with an ABA structure (polymer concentration 25% by weight). [Block copolymer (D)] In a nitrogen gas atmosphere, 0.1 part by weight of n-butyllithium was added to a cyclohexane solution containing 10 parts by weight of styrene, and after polymerization at 70°C for 1 hour,
A cyclohexane solution containing 80 parts by weight of isoprene was added and polymerized at 70°C for 2 hours. Thereafter, a cyclohexane solution containing 10 parts by weight of styrene was further added and polymerized at 70°C for 1 hour. The obtained polymer was a block copolymer of ABA structure with a styrene content of 20% by weight. To the block copolymer obtained above, 1,
3-dimethyl-2-imidazolidinone was reacted to obtain a terminally modified block copolymer (polymer concentration 20% by weight) in which the reactive residue of the compound was bonded to the polymer terminal. [Block copolymer (E)] In a nitrogen gas atmosphere, n-butyllithium was added to a cyclohexane solution containing 15 parts by weight of styrene and 0.06 parts by weight of tetramethylethylenediamine.
After adding 0.05 parts by weight and polymerizing at 70°C for 1 hour,
A cyclohexane solution containing 70 parts by weight of 1,3-butadiene was added and polymerized at 70°C for 2 hours. Thereafter, a cyclohexane solution containing 15 parts by weight of styrene was further added, and polymerization was carried out at 70°C for 1 hour. The obtained polymer was a block copolymer having an ABA structure with a styrene content of 30% by weight. Next, the block copolymer obtained above was hydrogenated using a Ti-based hydrogenation catalyst described in JP-A-59-133203 to obtain a hydrogenated block copolymer with a hydrogenation rate of 95% in the butadiene moiety ( A polymer concentration of 15% by weight) was obtained. [Block copolymer (F)] In a nitrogen gas atmosphere, 0.07 parts by weight of n-butyllithium was added to an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 20 parts by weight of styrene, and the mixture was heated at 70°C for 2 hours. After polymerization for an hour, an n-hexane solution containing 15 parts by weight of 1,3-butadiene and 50 parts by weight of styrene and 0.02 part by weight of n-butyllithium were further added, followed by polymerization at 70 DEG C. for 2 hours. The obtained polymer is a mixture of a B-A-B-A structure block copolymer and a B-A structure block copolymer with a styrene content of 70% by weight, and the obtained polymer solution is It was in the form of a suspension (polymer concentration 30% by weight). Examples 1 to 3 and Comparative Examples 1 to 6 In a cyclohexane solution of block copolymer (A),
Water was added as a reaction terminator in a molar amount 1.7 times the amount of n-butyllithium used in the polymerization, and the reaction was stopped by thorough mixing (first step). After that, 2,6-di-tert was added as a stabilizer. 1 part by weight of -butyl-4-methylphenol was added to 100 parts by weight of the block copolymer (A) (second step). This polymer solution was subjected to steam stripping under the conditions shown in Table 1 (third step). The concentration of polymer crumb in the slurry in the solvent removal tank was 2% by weight. Next, the water-dispersed slurry of the crumb-like block copolymer (A) obtained above was sent to a rotary screen to obtain a water-containing crumb having a water content of about 45% by weight. This water-containing crumb was sent to a single-screw extruder type water squeezer to obtain a polymer having the water content shown in the first example (fourth step). Then, the polymer obtained above was added to 2
Supplied to shaft single stage vented extruder, cylinder temperature
It was extruded and dried at 200°C, screw rotation speed of about 200 rpm, and vent pressure of about 200 mmHg (absolute pressure) (fifth step). The polymer obtained in the form of a strand from the tip of the extruder was cut into pellets using a cutter. Table 1 shows the water content, residual amount of lithium, transparency, and resistance to devitrification of the finally obtained polymer. As shown in Table 1, the block copolymer obtained by the method of the present invention had a small residual amount of lithium and was excellent in transparency and resistance to devitrification. It should be noted that the block copolymer obtained in Comparative Example 3 had an extremely poor color tone compared to those of Examples 1 to 3.

【table】

[Table] Comparative Example 7 A block copolymer was obtained in the same manner as in Example 2 except that a stabilizer was added before adding the reaction terminator. The obtained polymer had a residual lithium content of 52 ppm, and was not only inferior in transparency and devitrification resistance, but also had a poor color tone. Comparative Example 8 In the same manner as in Example 2, except that the block copolymer solution was diluted with cyclohexane so that the concentration was 5% by weight, and that solution was used in the third step. Steam stripped. As a result, agglomeration between crumbs was observed, and the crumb-forming performance was poor. Comparative Example 9 Same as Example 2, except that a solution obtained by flash evaporating cyclohexane so that the concentration of the block copolymer solution was about 75% by weight was used in the third step. Steam stripping was performed using the method described above. As a result, crumbs with particle diameters exceeding 50 mm were produced, and at the same time, aggregation among the crumbs was observed, making stable operation impossible. Comparative Example 10 Steam stripping was carried out in the same manner as in Example 2, except that the amount of crumbling agent added was 3000 ppm to the water in the stripping zone, but the foaming was severe and the solvent was removed. It was difficult to perform this stably. Examples 4 to 8 A solution of block copolymer (B) in cyclohexane,
After adding the reaction terminator shown in Table 2, octadecyl-3-(3,5-di-tert-butyl-4) was added as a stabilizer to 100 parts by weight of the block copolymer.
0.5 parts by weight of -hydroxyphenyl) propionate and 0.5 parts by weight of tris(2,4-di-tert-butylphenyl) phosphorite were added. When steam stripping the above block copolymer solution, a phosphoric acid ester in which A and B are hydrogen in the general formula [] is used as a crumbling agent, and A is hydrogen and B is R ₃ -O-( R ₄ -O) _-n (where R ₁ and R ₃ are p-nonylphenyl groups, R ₂ and R ₄ are ethylene groups, and n and m are each 9 or 10). Use 30ppm for water in the stripping zone, 90~
The solvent was removed at a temperature of 98°C. The concentration of polymer crumbs in the slurry in the solvent removal tank was approximately 5% by weight, and the crumbs were uniformly dispersed, not adhering to stirring blades, etc., and in a good dispersion state with no agglomeration between particles. It was hot. The water-dispersed slurry of the crumb-like block copolymer (B) obtained above was sent to a rotary screen to obtain a water-containing crumb having a water content of about 45% by weight. This water-containing crumb was fed to a two-stage slit, two-stage vented twin-screw extruder capable of performing dehydration and drying in the same device to obtain a pellet-like block copolymer. The extruder used was a screw type 40m/m,
One with an L/D ratio of 35 was used. The extrusion conditions were a cylinder temperature of 200℃ and a screw rotation speed of approximately 200 rpm.
minutes, the first vent was opened and the pressure was not reduced, and the second vent was vacuum vented to reduce the pressure to 50 mmHg absolute pressure. The water content after dehydration was determined by sampling a portion of the polymer from the first vent. The water content, residual amount of lithium, transparency, etc. of the obtained polymer were measured, and the results are shown in Table 2. As shown in Table 2, when an acid is used as a reaction terminator, a block copolymer with excellent color tone can be obtained. In particular, carbonated water and boric acid water have excellent transparency, resistance to devitrification, and color tone, and can be said to be effective reaction terminators.

[Table] Examples 9 and 10 Steam stripping of block copolymers (C) and (D) was carried out under the conditions shown in Table 3. The concentration of polymer crumb in the slurry in the solvent removal tank is approximately 10% by weight, and the crumb particle size is 0.2 to 30% by weight.
mm, the particles were in a good dispersion state with no agglomeration between them. The obtained water-containing crumb was dehydrated and dried in the same manner as in Examples 4 to 8 to obtain block copolymer pellets. Table 3 shows the water content etc. of the obtained polymer.

【table】

[Table] Example 11 As a crumbling agent, in the above general formula [], A and B are hydrogen, and A is hydrogen and B is _R3 -O-( _R4 -O) _-n. mixture with phosphoric acid ester (where R ₁ and R ₃ are p-nonylphenyl groups, R ₂ and R ₄ are ethylene groups, n and m
A solution of the block copolymer (E) in cyclohexane was steam-stripped in the same manner as in Example 7, except that 5, 6, or 7) was used at 50 ppm relative to the water in the stripping zone. The polymer solution used was one obtained by flash-evaporating cyclohexane after adding a stabilizer and having a concentration of 35% by weight. The concentration of polymer crumb in the slurry in the solvent removal tank is 8
% by weight, and the crumbs were uniformly dispersed and did not adhere to stirring blades or the like, and the particles were in a good dispersion state without agglomeration. The water-dispersed slurry of the crumb-like block copolymer (E) obtained above was sent to a rotary screen to obtain a water-containing crumb having a water content of about 50% by weight. This water-containing crumb was sent to a single-screw extruder type water squeezer to obtain a dehydrated crumb with a water content of 9% by weight. Thereafter, the water-containing crumb was sent to a single-screw type expander dryer to form a porous crumb, and further dried in a hot air dryer to obtain a polymer having a water content of 0.3% by weight. The resulting polymer had a residual lithium content of 15 ppm,
The polymer had a Haze of 6.2% and good devitrification resistance (rank ◎). Example 12 As a crumbling agent, in the general formula []
R ₁ is tridecyl group, R ₂ is ethylene group, n is 6,
A phosphate ester salt in which Me is sodium, and in the general formula [], R ₁ and R ₃ are tridecyl groups, R ₂ and R ₄ are ethylene groups, n and m are 6, and Me
A suspension of block copolymer (F) was steam-stripped, dehydrated, and dried in the same manner as in Example 7 using a mixture with a sodium phosphate ester salt. The crumbs were well dispersed in the solvent removal tank, and crumbs with a particle size of about 3 to 30 mm were obtained. The water content after dehydration is 3.8% by weight,
The moisture content of the final polymer after drying is 0.04
It was in weight%. In addition, the remaining amount of lithium is 18ppm,
It was a block copolymer with a Haze of 4.2%, excellent devitrification resistance (rank ◎), and excellent color tone.

Claims (1)

[Scope of Claims] 1. The vinyl aromatic hydrocarbon content is 5 to 95% by weight, obtained by polymerizing a conjugated diene and a vinyl aromatic hydrocarbon in a hydrocarbon solvent using an organolithium compound as an initiator. In obtaining a block copolymer or its hydrogenated product by steam stripping the solvent from a solution of the block copolymer or its hydrogenated product, a combination of the following steps (1) to (5) is performed. A method for obtaining a block copolymer or a hydrogenated product thereof having a residual amount of lithium of 40 ppm or less. (1) A step of adding at least one reaction terminator selected from (a) water, (b) alcohol, (c) inorganic acids, and (d) organic acids to a solution of the block copolymer or its hydrogenated product. (2) A step of adding a stabilizer to the solution of the block copolymer or its hydrogenated product. (3) A solution of the block copolymer or its hydrogenated product having a polymer concentration of 10 to 60% by weight is mixed with the following phosphate ester (e) and/or phosphate ester salt (f) from 0.1 to 0.1%.
In the presence of 1000 ppm (weight ratio of the stripping zone to water), the boiling point of the hydrocarbon solvent or the azeotropic temperature if the solvent and water are azeotropic,
A process of stripping at a temperature below 120°C to obtain a slurry in which crumb-like polymers are dispersed in water. (e) one selected from the group consisting of polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkylaryl ether phosphate, and polyoxyalkylene alkenyl aryl ether phosphate; or Two or more phosphoric acid esters (f) Alkali of polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkenyl ether phosphate, polyoxyalkylene alkylaryl ether phosphate, and polyoxyalkylene alkenyl aryl ether phosphate One or more phosphate ester salts selected from the group consisting of metal salts and ammonium salts. (4) The moisture-containing block copolymer or its hydrogenated crumb obtained above is dehydrated to reduce the moisture content to 1.
Process to make ~30% by weight. (5) Drying the block copolymer or its hydrogenated product obtained above to reduce the water content to less than 1% by weight.