JPH0713090B2 - Recovery method of polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxial method for directly removing a solvent from a solution of a block copolymer of a conjugated diene and a vinyl aromatic hydrocarbon or a hydrogenated product thereof. The present invention relates to a method for efficiently removing a solvent using a vent extruder.

[Conventional technology]

A block copolymer composed of a conjugated diene and a vinyl aromatic hydrocarbon is transparent and has a similar content to vulcanized natural rubber or synthetic rubber without vulcanization when the vinyl aromatic hydrocarbon content is relatively low. Since it has elasticity at room temperature and has the same processability as a thermoplastic resin at high temperature, it is widely used in the fields of footwear, plastic modification, asphalt, adhesive bonding and the like. Further, when the content of vinyl aromatic hydrocarbons is relatively high, a transparent thermoplastic resin having excellent impact resistance can be obtained, so that the amount of its use has increased in recent years mainly in the field of food packaging containers, and at the same time, it has applications. It is diversifying.

When producing these copolymers, the polymerization is usually carried out in a hydrocarbon solvent which is inert to the catalyst, and the produced copolymer is uniformly melted or suspended in the solvent. Since it is obtained, the copolymer and the solvent are separated,
A step of recovering the copolymer is required. There are various methods for separating the copolymer and the solvent, and as one of them, a method of directly removing the solvent from the polymer solvent is known. For example, JP-A-50-76172 and JP-B-5
1-6105, Japanese Patent Publication 57-47685, Japanese Patent Publication 57-51
Japanese Patent No. 407 and the like describe a method of directly desolvating a solvent from a solution of rubber, plastic, or a block copolymer by using a twin-screw vent extruder.

[Problems to be Solved by the Invention]

The direct desolvation method using the twin-screw vent extruder as described above is
Although there is a practical advantage that the device is compact and the operation is relatively simple, the polymer is bent up at the vent part, and the fine powdery polymer is scattered in the vacuum degassing line, and the vent is up. The generated polymer or scattered polymer causes blockage in the vacuum degassing line or the vacuum system, which reduces the degassing ability and causes a problem that a polymer with little residual solvent cannot be stably produced for a long time. It was

[Means for Solving the Problems]

The inventors of the present invention have conducted a diligent study to solve the above-mentioned drawbacks of the prior art in a method of directly desolvating a solvent from a polymer solution using a twin-screw vent extruder, and as a result, have a specific lead as a screw in a vent section. The present invention has been completed by using a screw and by finding that the F factor in the vent portion defined in the present invention can be achieved by degassing under reduced pressure under a specific condition.

That is, the present invention, in a hydrocarbon solvent, the solvent directly from the solution of a block copolymer or a hydrogenated product thereof obtained by block-copolymerizing a conjugated diene and a vinyl aromatic hydrocarbon with an organolithium compound as an initiator. When the block copolymer or the hydrogenated product thereof is obtained by desolvation, a twin-screw vent extruder is used, and (1) the screw lead of the screw of the vent section of the vent extruder is 0.75 × D to 2 A screw having a structure of × D (where D is the outer diameter of the screw) is used.

(2) The vent section of the vent extruder is degassed under reduced pressure under the condition that the F factor defined by the following formula is 0.8 or less.

(In the above formula, V is the evaporation rate [m ³ / hr] of the solvent in the vent part, W is the evaporation amount of the solvent in the vent part [kg / hr], and A is the opening area of the vent part [m ² ].) The present invention relates to a method for recovering a featured block copolymer or a hydrogenated product thereof.

Hereinafter, the present invention will be described in detail.

The vinyl aromatic hydrocarbon content of the block copolymer of the conjugated diene and vinyl aromatic hydrocarbon used in the present invention or the hydrogenated product thereof is generally 5 to 95% by weight, preferably 10 to
90% by weight.

Examples of the method for producing the block copolymer include, for example, Japanese Patent Publication Sho 36
-19286, Japanese Patent Publication No. 43-17979, Japanese Patent Publication No. 46-32
415, JP-B-49-36957, JP-B-48-2423, JP-B-48-4106, JP-B-56-28925, JP-B-51-49567, JP-A-59-166518. The methods described in JP-A No. 60-186577 and JP-A No. 60-186577 are mentioned. According to these methods, the block copolymer is represented by the general formula: (AB) n, AB-A) n, BA-B) n (wherein A is a polymer block mainly composed of vinyl aromatic hydrocarbons). And B is a polymer block mainly composed of a conjugated diene. The boundary between the A block and the B block does not necessarily have to be clearly divided, and n is an integer of 1 or more.) Or general Formula [(B-Anm ₊₁ X, [(A-Bnm ₊₁ X, [(B-AnBm ₊₁ X, [(A-BnAm ₊₁ X (wherein A and B are the same as the above. , X is, for example, a residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, an epoxidized soybean oil, a polyhalogenated hydrocarbon, a carboxylic acid ester or a polyvinyl compound, or a residue of an initiator such as a polyfunctional organolithium compound. Where m and n are integers of 1 or more.) In the above formula, the polymer block mainly containing vinyl aromatic hydrocarbon means a copolymer block of vinyl aromatic hydrocarbon and conjugated diene containing 50% by weight or more of vinyl aromatic hydrocarbon. And / or a vinyl aromatic hydrocarbon homopolymer block, and a polymer block containing a conjugated diene as a main component means a copolymerization weight of a conjugated diene containing a conjugated diene in an amount of more than 50% by weight and a vinyl aromatic hydrocarbon. Shows a polymer block and / or a conjugated diene homopolymer block, even if the vinyl aromatic hydrocarbon in the copolymer block is evenly distributed,
Further, it may be distributed in a taper shape. Further, in the copolymer portion, a plurality of portions in which vinyl aromatic hydrocarbons are evenly distributed and / or a portion in which taper distribution is formed may coexist. The block copolymer used in the present invention may be any mixture of the block copolymers represented by the above general formula.

The block copolymer thus obtained has a vinyl aromatic hydrocarbon content of 60% by weight or less, preferably 55% by weight.
The following cases show characteristics as a thermoplastic elastic body, and a vinyl aromatic hydrocarbon content of more than 60% by weight, preferably 65% by weight or more, shows characteristics as a thermoplastic resin.

Examples of the vinyl aromatic hydrocarbon used in the method of the present invention are styrene, o-methylstyrene, p-methylstyrene, p
-Tert-butylstyrene, 1,3-dimethylstyrene, α
-Methyl styrene, vinyl naphthalene, vinyl anthracene, etc., but styrene is particularly common. These 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, and examples thereof include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3.
-Dimethyl-1,3-butadiene, 1,3-pentadiene, 1,
Although 3-hexadiene and the like are mentioned, particularly common ones are 1,3-butadiene and isoprene. These may be used alone or in combination of two or more.
As the hydrocarbon solvent used in the production of the block copolymer, butane, pentane, hexane, isopentane, heptane, octane, aliphatic hydrocarbons such as isooctane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane and the like. Alicyclic hydrocarbons or aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene can be used. These may be used alone or in combination of two or more. The organolithium compound used in the production of the block copolymer is an organomonolithium compound having one or more lithium atoms bonded in the molecule, such as ethyllithium, n-propyllithium, isopropyllithium, n-butyl. Lithium, sec-butyllithium, tert
-Butyl lithium, hexamethylene dilithium, butadienyl dilithium, isoprenyl dilithium and the like. These may be used alone or in combination of two or more.

In the production of the block copolymer used in the present invention, the polymerization rate is adjusted, the microstructure of the polymerized conjugated diene part (ratio of cis, trans, vinyl) is changed, and the reactivity ratio between the conjugated diene and the vinyl aromatic hydrocarbon is adjusted. A polar compound or a randomizing agent can be used for the purpose of adjusting the above. As polar compounds and randomizing agents, ethers, amines,
Examples thereof include 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, diethylene glycol dibutyl ether.
As amines, tertiary amines such as trimethylamine, triethylamine, tetramethylethylenediamine, and cyclic tertiary amines can be used. Phosphines and phosphoramides include triphenylphosphine and hexamethylphosphoramide. Examples of the randomizing agent include potassium or sodium alkylbenzene sulfonate, potassium or sodium butoxy, and the like.

The polymerization temperature in producing the block copolymer in the present invention is generally -10 ° C to 150 ° C, preferably 40 ° C to 1
20 ° C. The time required for polymerization varies depending on the conditions, but is usually within 48 hours, particularly preferably 0.5 to 1
It's 0 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 the range of the above-mentioned polymerization temperature and is a pressure sufficient to maintain the monomer and the solvent in the liquid phase. Further, it is necessary to take care so that impurities that inactivate the catalyst and the living polymer, such as oxygen and carbon dioxide, do not enter the polymerization system.

The number average molecular weight of the block copolymer thus obtained is generally 10,000 to 1,000,000, preferably 20,000 to 80.
It is 0,000, more preferably 30,000 to 500,000. The amount of hydrocarbons in the block copolymer solution is generally 10
150 to 2000 parts by weight with respect to 0 parts by weight. Incidentally, depending on the properties of the block copolymer, the block copolymer may be obtained in a state of being insoluble in a hydrocarbon solvent, but in the present invention, these are also called block copolymer solutions. .

As the block copolymer used in the present invention, an end-modified block copolymer in which a polar group-containing atomic group is engaged with at least one polymer chain end of the polymer can be used. Here, the polar group-containing atomic group means an atomic group containing at least one atom selected from nitrogen, oxygen, silicon, phosphorus, 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, sulfonate group, phosphate group,
Phosphate group, amino group, imino group, nitrile group,
At least a polar group selected from a pyridyl group, a quinoline group, an epoxy group, a thioepoxy group, a sulfide group, an isocyanate group, an isothiocyanate group, a silicon halide group, an alkoxysilicon group, a tin halide group, an alkyltin group, a phenyltin group, and the like. One example is an atomic group containing one kind. More specifically, the terminal modified block copolymer described in Japanese Patent Application No. 60-224806 can be used.

In the present invention, the block copolymer or modified block copolymer obtained above can be partially or selectively hydrogenated by a hydrogenation reaction (hydrogenation reaction). The hydrogenation rate can be arbitrarily selected, and in order to improve the heat deterioration resistance while maintaining the characteristics of the unhydrogenated polymer, the aliphatic double bond based on the conjugated diene is 3% or more, 80% or more.
%, Preferably 5% or more and less than 75% Hydrogenated, or 80% to improve heat deterioration resistance and weather resistance
It is recommended to hydrogenate the above, preferably 90% or more.
In this case, water of an aromatic double bond based on the vinyl aromatic compound copolymerized with the polymer block A mainly containing the vinyl aromatic compound and, if necessary, the polymer block B mainly containing the conjugated diene compound. The addition rate is not particularly limited, but the hydrogen addition rate is preferably 20% or less. The amount of unhydrogenated aliphatic double bonds contained in the hydrogenated block copolymer can be easily known by an infrared spectrometer, a nuclear magnetic resonance apparatus or the like. As the catalyst used in the hydrogenation reaction, (1) a supported heterogeneous catalyst in which a metal such as Ni, Pt, Pd, Ru is supported on carbon, silica, alumina, diatomaceous earth, and (2) Ni Known are homogeneous catalysts such as so-called Ziegler type catalysts that use organic acid salts such as Co, Fe, Cr or acetylacetone salts and reducing agents such as organic Al, or so-called organic complex catalysts such as organic metal compounds such as Ru and Rh. Has been. As a specific method, Japanese Examined Patent Publication No. 42-8704,
According to the method described in JP-B-43-6636 or JP-A-59-133203, JP-A-60-220147,
Hydrogenating in the presence of a hydrogenation catalyst in an inert solvent,
A hydrogenated product can be obtained to synthesize the hydrogenated block copolymer used in the present invention. At that time, the hydrogenation rate of the aliphatic double bond based on the conjugated diene compound in the block copolymer can be controlled to an arbitrary value by adjusting the reaction temperature, the reaction time, the hydrogen supply amount, the catalyst amount and the like.

To the solution of the block copolymer or hydrogenated product thereof obtained as described above, generally at least one reaction terminator having active hydrogen is added before desolvation. Examples of the compound having active hydrogen include water, alcohols, thiols, amines, inorganic acids, organic acids and the like. In the present invention, at least one selected from (a) water, (b) alcohol and (c) organic acid. One reaction terminator is preferred. 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. Further, the organic acid used in the present invention is an organic compound having acidity in a broad sense, and examples thereof include compounds such as carboxylic acid, sulfonic acid, sulfinic acid, and phenol, but preferably an organic compound containing a carboxyl group. The following are preferred.

(1) Fatty acids having 8 or more carbon atoms (2) Rosin acid (3) Oxycarboxylic acid (4) Aromatic carboxylic acid A particularly preferred organic acid is the fatty acid of (1), and specific examples thereof include octyl acid, capric acid, Examples thereof include lauric acid, myristic acid, barmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, behenic acid, castor-hardened fatty acid, tallow fatty acid, or a mixture thereof.

The amount of these reaction terminators added is generally equimolar or more, preferably 1.5 moles or more, based on the total amount of the reaction terminator based on the organolithium compound used for the polymerization. When the reaction terminator is water and alcohol, the addition amount is preferably 1.5.
The amount is from mol to 1000 mol, and more preferably from 2.0 mol to 500 mol. When the reaction terminator is an organic acid, the addition amount is preferably
The amount is 0.05 to 10 mol, more preferably 0.2 to 5 mol. If the addition amount of the organic acid is less than this mole, another reaction terminator,
It is preferable to use it in combination with water so that the total amount of the reaction terminator becomes equimolar or more. The reaction terminator particularly suitable in the present invention is at least one selected from alcohols and fatty acids.

Further, the solution of the block copolymer or the hydrogenated product thereof to which the reaction terminator is added may be adjusted to pH by adding an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, carbon dioxide gas or the above-mentioned organic acid, if necessary. 4-10, preferably 5-9, more preferably 6-
Adjusted to a range of 8. Incidentally, the pH of the solution of the block copolymer or the hydrogenated product here, a part of the solution is collected,
The pH of the aqueous layer obtained by thoroughly mixing the solution with distilled water (pH 7.0 ± 0.5) having the same weight as that of the solution and then leaving the mixture to stand is indicated. The pH can be measured using a glass electrode type hydrogen ion concentration meter (pH meter). In the present invention, carbon dioxide gas is preferable for adjusting the pH to the above range, and the carbon dioxide gas is added to the solution of the block copolymer or its hydrogenated product in the gas state (a) and mixed,
It is preferably added by a method of dissolving or (b) adding to the solution in a state of being dissolved in a hydrocarbon solvent or a solvent soluble in a hydrocarbon solvent and mixing. Such an addition method is more preferable than a method of adding carbonated water in order to obtain a polymer having a good color tone and hot water whitening resistance. The apparatus for mixing the solution of the polymer or hydrogenated product thereof with the carbon dioxide gas or the solution thereof by the above method is not particularly limited and any known apparatus can be used. For example, a stirrer blade type container mixer, a line mixer such as a static mixer, a homomixer, or the like can be used. The same solvent as the hydrocarbon solvent that dissolves carbon dioxide can be used. Further, as a solvent soluble in a hydrocarbon solvent, halogenated hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride, ethers such as ethyl ether, tetrahydrofuran and trioxane, ketones such as acetone and methyl ethyl ethone, and methyl acetate. , Esters such as methyl propionate, nitrogen-containing compounds such as nitrobenzene and aniline, sulfur-containing compounds such as dimethyl sulfoxide and propane sultone, and the like can be used.
Of these solvents, it is preferable to use the same solvent as the hydrocarbon solvent used for polymerizing the polymer.

A reaction terminator is added as described above, and if necessary,
A stabilizer is added to the solution of the pH-adjusted block copolymer or its hydrogenated product. Addition of the stabilizer at this stage is effective in preventing the polymer from undergoing oxidative deterioration or thermal deterioration when the solvent is removed in the next step. These may be added to the polymer solvent as they are, or may be dissolved in a hydrocarbon solvent and added. The stabilizer may be any known stabilizer that has been used in the past, a phenol-based, an organic phosphate-based, an organic phosphite-based,
Various known antioxidants such as amine type and sulfur type are used. Stabilizers are generally 0.001 per 100 parts by weight of polymer.
Used in the range of up to 10 parts by weight. In the present invention, the stabilizer may be added at the same time as the reaction terminator or pH adjuster.

Next, the solution of the block copolymer or the hydrogenated product obtained above is desolvated, and the solution has a polymer concentration of 50 to 98 wt% by a concentrator before being fed to the twin-screw vent extruder. %,
Preferably 70-96% by weight, more preferably 80-94% by weight
It is generally concentrated to a concentration of. When the polymer concentration concentrated in the concentrator is less than 50% by weight, it is difficult to obtain a polymer with little residual solvent due to insufficient desolvation in a twin-screw vent extruder, and when the concentration exceeds 98% by weight. Makes it difficult to transfer the polymer solution from the concentrator to the twin-screw vent extruder. As the concentrator, a flash tank type concentrator, a stirred tank concentrator, a thin film evaporation type concentrator, a wet-wall mounted type concentrator, etc. capable of multi-stage concentrating in one or more stages can be used. The polymer solution fed to the concentrator is generally 120-250 ° C, preferably
Preheated to 150-220 ° C. If the preheating temperature is less than 120 ° C, the concentration in the concentrator will be insufficient and the preheating temperature will
If the temperature exceeds 250 ° C, problems such as gelation of the polymer occur, which is not preferable.

Next, the block copolymer or the solution thereof concentrated as described above is a biaxial vent extrusion having at least one degassing vent portion, preferably 2 to 10, and more preferably 3 to 5. It is supplied to the machine and the solvent is degassed under reduced pressure from the vent. As a vent extruder having such a structure, L / D = 10 to 50,
It is preferably about 15 to 40 (L is the length of the screw, D is the outer diameter of the screw), and the screw engagement structure can be either meshing or non-meshing, and the rotation directions are the same. , In different directions.

One of the features of the present invention is that the screw lead of the screw of the vent portion is 0.75 × D to 2 × D, preferably 1.0 × D to 1.75.
A screw having a structure of xD, more preferably 1.25xD to 1.5xD is used. 0.75 screw leads
If it is less than × D, the polymer is likely to vent up in the vent portion, making stable operation for a long period of time impossible. or,
If the screw lead exceeds 2 × D, the drying will be insufficient,
A polymer having a low water content cannot be obtained. Here, the lead in the present invention means a distance that the screw thread moves in the axial direction per one rotation of the screw. The groove depth H of the screw in the vent portion is generally 0.1 × D to 0.25 × D, preferably 0.12 × D to 0.2 × D, and the number of threads of the screw is generally 1 to 3.

In the present invention, the screw rotation speed of the twin-screw vent extruder, the cylinder heating temperature, and the pressure of the vent portion are selected in consideration of the extrusion capacity, the characteristics of the polymer (viscosity and thermal stability), the quality of the product, etc. Generally, the screw rotation speed is 20 to 500 rotations / minute, preferably 30 to 400 rotations / minute, and the cylinder temperature is 1
00-300 ℃, preferably 130-260 ℃, vent pressure 5
~ 500 mmHg absolute pressure, preferably 10 ~ 400 mmHg absolute pressure range, in the present invention, in the vent portion, the F factor defined above is 0.8 or less, preferably 0.05 to 0.75, more preferably 0.1 ~. It must be degassed under reduced pressure under conditions of 0.6. If the F factor exceeds 0.8, the amount of the finely divided polymer scattered at the vent portion increases, which is not preferable. In order to reduce the F factor to less than 0.05, it is necessary to make the vent portion high vacuum or to make the opening area of the vent portion extremely wide. Therefore, it is generally recommended to set the F factor in the range of 0.05 to 0.8. . In calculating the F factor, V is obtained from the following equation.

(In the above formula, W is the evaporation amount [kg / hr] of the solvent in the vent part, M is the molecular weight [kg / kmol] of the solvent. When the solvent is a mixture of two or more hydrocarbons, M is It is the sum of (molar fraction of each component) × (molecular weight of each component).
Is a gas constant of 0.082 m ³ · atom / kmol · ° K, T is a cylinder temperature [° C] at the vent, and P is a pressure at the vent [mmHg absolute pressure]. ) W is the amount of the polymer solution supplied to the vent section M ₀ [kg
/ hr], the proportion of the solvent in the polymer solution f ₀ [polymerization%], the amount of the polymer after degassing treatment at the vent M ₁ [kg / hr], in the polymer after the degassing treatment The ratio f ₁ [polymerization%] of the residual solvent can be measured and calculated from W = M ₀ × f ₀ −M ₁ × f ₁ . The cylinder temperature at the vent is
Generally, it is 130 to 260 ° C, preferably 150 to 230 ° C.

Further, in the present invention, a twin-screw extruder having two or more vent parts is used, and the pressure of the vent part of the first-stage vent near the supply of the polymer solution is 50 to 500 mmHg absolute pressure, preferably 100 to 40
It is recommended to set 0 mmHg absolute pressure and set the pressure of the vent portion after the second stage vent to 5 to 200 mmHg absolute pressure, preferably 10 to 100 mmHg absolute pressure.

The amount of residual solvent in the dried polymer directly recovered by the method of the present invention and recovered is less than 1% by weight, preferably 0.5% by weight or less, and more preferably 0.2% by weight or less. When the amount of residual solvent in the dried polymer is 1% by weight or more, it is not preferable because foaming occurs when the polymer is molded and appearance defects such as silver occur. The polymer desolvated by the twin-screw vent extruder can be obtained in the form of foamed crumb, granules or powder, or in the form of strands or pellets.

In the method of the present invention, in order to more effectively carry out desolvation in the twin-screw extruder, the polymer solution supplied to the twin-screw extruder and / or water at the inlet or in the middle of the twin-screw extruder. Can be added. Water is generally added in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the polymer solution.

In the method of the present invention, various additives may 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 fibers / inorganic fibers, reinforcing agents such as carbon black, and other thermoplastic resins may be used. It can be used as an additive. These additives may be added to the polymer solution, or may be added to the polymer solution after being concentrated in a concentrator and / or at the entrance of the twin-screw vent extruder or in the middle thereof.

By the method of the present invention, the solvent removal treatment of a solution of a block copolymer obtained by block copolymerizing a conjugated diene and a vinyl aromatic hydrocarbon or a hydrogenated product thereof can be carried out efficiently and smoothly. Further, the polymer obtained by the method of the present invention is transparent and excellent in color tone, and therefore, by utilizing its characteristics, various types such as sheets, films, injection molded products of various shapes, hollow molded products, pressure molded products, vacuum molded products, etc. It can be used as a versatile molded product, as well as various thermoplastic resin modifiers, footwear materials, adhesives, etc.
Adhesive material, asphalt modifier, wire cable material, vulcanized rubber material, vulcanized rubber modifier, home appliances
It can be used for materials such as automobile parts, industrial parts, household items and toys.

〔Example〕

Hereinafter, the present invention will be described more specifically with reference to examples.
The block copolymer used in the examples was manufactured as follows. Obtained block copolymers (A) to (C)
In the polymer solution of, the weight ratio of the polymer and the solvent is 1:
Was 3.

[Block copolymer (A)]

In a nitrogen gas atmosphere, a cyclohexane solution containing 30 parts by weight of styrene and 0.3 parts by weight of tetrahydrofuran was added to the solution.
-Add 0.08 parts by weight of butyl lithium and polymerize at 70 ° C for 1 hour, then add 20 parts by weight of 1,3-butadiene and 50 parts of styrene.
A cyclohexane solution containing 1 part by weight was added and polymerization was carried out at 70 ° C. for 2 hours. The obtained polymer was a block copolymer having an ABA structure with a styrene content of 80% by 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, polymerized at 70 ° C. for 1 hour, and then a cyclohexane solution containing 25 parts by weight of 1,3-butadiene was added. Polymerization was carried out at 70 ° C for 2 hours. Then, 5 parts by weight of epoxidized soybean oil was added to obtain a block copolymer having a styrene content of 75% by weight and having a radical structure.

[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 polymerized at 70 ° C. for 2 hours. -An n-hexane solution containing 45 parts by weight of butanediene and 20 parts by weight of styrene was added and the mixture was polymerized at 70 ° C for 2 hours. The polymer obtained is a B having a styrene content of 40% by weight.
It was a block copolymer having a -A-B-A structure.

[Block copolymer (D)]

In a nitrogen gas atmosphere, 0.1 part by weight of n-butyllithium was added to a cyclohexane solution containing 10% by weight of styrene, and the mixture was polymerized at 70 ° C. for 1 hour. Then, a cyclohexane solution containing 80 parts by weight of isoprene was added at 70 ° C. Polymerized for 2 hours. Then, a cyclohexane solution containing 10 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 20% by weight [polymer concentration 20% by weight].

[Block copolymer (E)]

In a nitrogen gas atmosphere, 0.06 parts by weight of n-butyllithium was added to a cyclohexane solution containing 15 parts by weight of styrene and 0.06 parts by weight of tetramethylethylenediamine and heated to 70 ° C.
After polymerizing for 1 hour at 70 ° C., a cyclohexane solution containing 70 parts by weight of 1,3-butadiene was added and the mixture was polymerized at 70 ° C. for 2 hours.
Then, 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 is
It was an ABA structural block copolymer having a styrene content of 30%.

Next, the block copolymer obtained as described above was treated with JP-A-59-13.
Hydrogenated block copolymer hydrogenated with a Ti-based hydrogenation catalyst described in 3203 and having a butadiene portion hydrogenation rate of 95% (concentration of polymer
15% by weight).

[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 polymerized at 70 ° C. for 2 hours, followed by 1,3-butadiene. An n-hexane solution containing 15 parts by weight and 50 parts by weight of styrene and 0.02 part by weight of n-butyllithium were added, and polymerization was carried out at 70 ° C. for 2 hours. The polymer obtained was a mixture of a block copolymer having a B-A-B-A structure having a styrene content of 70% by weight and a block copolymer having a B-A structure, and the obtained polymer solution ( The polymer concentration was 30% by weight) in the form of suspension.

Examples 1 and 2 and Comparative Examples 1 and 2 To the cyclohexane solution of the block copolymer (A), water was added as a reaction terminator in an amount of 50 times the molar amount of butyllithium used in the polymerization, and mixed sufficiently to stop the reaction. After that, carbon dioxide gas was added to the solution in a gas state to adjust the pH of the solution to about 7.

Next, with respect to 100 parts by weight of the block copolymer, 0.5 parts by weight of octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate and tris (2,4-
0.5 parts by weight of di-tert-butylphenyl) phosphite was added and mixed well.

After heating the above polymer solution through a heat exchanger to about 200 ° C, introduce it to a cylindrical flash tank type concentrator, flash evaporate a part of the solvent and concentrate the polymer concentration to about 90% by weight. A polymer solution was obtained. Then, the concentrated polymer solution was supplied to a twin-screw two-stage vent extruder, and the solvent was degassed under reduced pressure from the vent. The twin-screw vent extruder used has a screw outer diameter
40 mm, L / D was 38.5, and the screw rotation speed was about 300 rpm. The dried polymer obtained in a strand form from the tip of the extruder was pelletized by a cutter. The lead of the vent screw, the opening area of the vent, and the extrusion rate were set to the conditions shown in Table 1.

The results are shown in Table 1. In addition, Example 1 was repeated except that the neutralization treatment with carbon dioxide gas was not performed at all after adding the reaction terminator.
Desolvation of the block copolymer (A) was carried out in the same manner as in Example 1. Desolvation operation could be carried out smoothly as in Example 1, and a polymer having a residual solvent amount of about 0.25% by weight was obtained. However, the color of the pellet was yellow and the color tone (b value of 4.5) was poor.

The vinyl aromatic hydrocarbon content in the polymer is 60% by weight.
In the following cases, use a compression molded plate with a thickness of 2 mm, and if the vinyl aromatic hydrocarbon content exceeds 60% by weight,
A 2 mm injection molded plate was used.

Comparative Example 3 In Example 1, the lead of the screw in the vent portion was 0.
The block copolymer (A) was desolvated under the same conditions as in Example 1 except that a screw of 5 × D was used.
However, under such conditions, the venting at the vent portion was so severe that normal operation could not be performed.

Comparative Example 4 In Example 1, the lead of the screw in the vent part was 3.
The block copolymer (A) was desolvated under the same conditions as in Example 1 except that a screw of 0 × D was used.
However, under such conditions, degassing at the vent was insufficient, and the amount of residual solvent of the polymer extruded from the tip of the extruder exceeded 1% by weight, which was unsuitable as a product.

Example 3 The solvent of the block copolymer (D) solution was desolvated in the same manner as in the stabilizer 1. In Example 3, benzoic acid was used as a reaction terminator in an equimolar amount with respect to butyllithium used in the polymerization, and 2,4-bisbis was used as a stabilizer with respect to 100 parts by weight of the block copolymer. 0.5 parts by weight of-(n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine and 1.0 parts by weight of trisnonylphenylphosphato were added. As the screw of the vent portion in the first-stage vent and the second-stage vent, a screw with a lead of 1.5 × D was used. The F factor in the 1st stage vent is And the F factor at the second stage vent is Met. There was almost no scattering of the polymer fine powder to the vent pipe at each vent, and stable operation could be performed. The amount of residual solvent in the obtained dried polymer was about 0.23% by weight, and the color tone (b value of 1.6) was good.

Examples 4,5 and Comparative Examples 5 and 6 To the cyclohexane solvent of the block copolymer (C), methanol was added as a reaction terminator in an amount of 2 times the molar amount of butyllithium used in the polymerization, and the mixture was sufficiently mixed to terminate the reaction. After that, carbon dioxide gas previously dissolved in cyclohexane was added to the solution and mixed well. The pH of the solution was adjusted to about 7.5.

Next, with respect to 100 parts by weight of the block copolymer, 2-tert
-Butyl-6- (3-tert-butyl-2-hydroxy-
0.2 parts by weight of 5-methylbenzyl) -4-methylphenyl acrylate and 0.1 parts by weight of tris (2,4-di-tert-butylphenyl) phosphite were added and mixed well.

After heating the above polymer solution through a heat exchanger to about 180 ° C, it is introduced into a cylindrical flash tank type concentrator, and part of the solvent is flash evaporated to concentrate the polymer concentration to about 90% by weight. A polymer solution was obtained. Then, about 1 part by weight of water was added to the concentrated polymer solution based on 100 parts by weight of the polymer solution, and the mixture was supplied to a twin-screw three-stage vent extruder to degas the solvent from each vent under reduced pressure. The twin-screw vent extruder used has a screw outer diameter of 40 mm, an L / D of 45.5, and a screw rotation speed of about 160.
It was driven at rpm. The dried polymer obtained in a strand form from the tip of the extruder was pelletized by a cutter. The screw leads of each vent screw, each vent opening area,
The cylinder temperature and the extrusion rate of each vent were set to the conditions shown in Table 2.

The results are shown in Table 2.

Examples 6 to 8 Under the conditions shown in Table 3, the block copolymers (B), (E) and (F) were directly desolvated in the same manner as in Example 4. The reaction terminator was added in an amount of 5 times the molar amount of butyllithium used for the polymerization.

The results are shown in Table 3.

[Effect of the Invention] By the method of the present invention, desolvation treatment of a block copolymer obtained by block copolymerizing a conjugated diene and a vinyl aromatic hydrocarbon or a hydrogenated product thereof can be carried out efficiently and smoothly.

Claims (1)

[Claims] 1. A solvent is directly removed from a solution of a block copolymer obtained by block copolymerizing a conjugated diene and a vinyl aromatic hydrocarbon with an organolithium compound as an initiator in a hydrocarbon solvent or a hydrogenated product thereof. When collecting the block copolymer or its hydrogenated product as a solvent, a twin-screw vent extruder is used, and (1) the screw lead of the screw at the vent part of the vent extruder is 0.75 × D to 2 × A screw having a structure of D (where D is the outer diameter of the screw) is used, and (2) the vent portion of the vent extruder is degassed under reduced pressure under the condition that the F factor defined by the following formula is 0.8 or less. A method for recovering a block copolymer or a hydrogenated product thereof. (In the above formula, V is the evaporation rate of the solvent in the vent part [m ³ / hr] W is the evaporation amount of the solvent in the vent part [kg / hr] A is the opening area of the vent part (m ² ).)