JP2004339281A - Preparation method for block copolymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing a block copolymer by obtaining a crumb-like block copolymer through steam stripping and subjecting it to dehydration and solvent removal, wherein dehydration and solvent removal are efficiently conducted to yield the block copolymer having a low final concentration of a residual solvent and a quality (e.g. little amount of granular structure, transparency) required for its application to a sheet, a film, or the like. <P>SOLUTION: In the preparation method for the block copolymer, a hydrocarbon solvent solution of a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene is subjected to steam stripping to obtain the crumb-like block copolymer. Then, the crumb-like block copolymer is dehydrated and hot-air dried at 70-95°C to achieve a moisture content of 5-20 mass% before being extruded from a biaxial extruder equipped with a deaerating slit and a deaerating vent part having a depressurizing means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５０】
【表２】

【００５１】
【発明の効果】
本発明によれば、予め適度の脱水、乾燥を行った後、２軸押出機に供給し、脱水と脱溶剤を行うことにより、残存溶媒量の少ないブロック共重合体を効率的に取得できる製造方法が提供される。得られるブロック共重合体は、ブツが少なく、透明性、色調に優れるため、シート、フィルム、各種形状の射出成形品、真空成形品、圧空成形品、あるいは、工業部品、家庭用品、玩具等の素材としても利用できる。特に、本発明で得られるブロック共重合体は、残存溶媒量が少なく、透明性にも優れ、ゲル分も少ないため、医療用品、食品容器、食品包装材、飲料ボトル等のラベル等の用途に有効である。
【００５２】
【図面の簡単な説明】
【図１】本発明の請求項１を説明するための工程概略図である。
【図２】本発明の請求項２を説明するための工程概略図である。
【符号の説明】
１；押出機
２；供給ホッパー
３；２軸スクリュー
４；脱気用のスリット
５；ベント部
６；ダイ
７；脱水用のスリット[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a block copolymer having a low residual solvent concentration after steam stripping the solvent from a block copolymer solution comprising a vinyl aromatic hydrocarbon and a conjugated diene, followed by dehydration and desolvation with a twin-screw extruder. It is related to a method of acquiring efficiently.
[0002]
[Prior art]
Block copolymers composed of vinyl aromatic hydrocarbons and conjugated dienes are resins with transparency and impact resistance, and since stretched sheets and films exhibit heat shrinkage, sheets, films, and various shapes Used for applications such as injection molded products. In the production of this block copolymer, polymerization is generally carried out in a hydrocarbon solvent which is inert to the catalyst, and the resulting block copolymer is dissolved in the solvent. Requires a step of separating them.
As one of the methods, a method is known in which a polymer solution is supplied into hot water, the solvent is removed by steam stripping, and the polymer is precipitated in a crumb shape. The crumb-shaped block copolymer obtained by such a method is further subjected to dehydration and drying treatment, and is granulated into pellets. Furthermore, a method of removing water by a twin-screw vent extruder is described (for example, see Patent Documents 1 and 2).
[0003]
However, the slurry containing the crumb obtained by the steam stripping method is dewatered, and the wet crumb after the dewatering is supplied to the twin-screw extruder without drying in advance, and the block copolymer obtained by the method of drying and removing the solvent is used. Coalescing is not sufficient in terms of quality, particularly in terms of prevention of lumps, reduction of residual solvent concentration, and balance of production efficiency. Particularly, in order to evaporate and remove the water and residual solvent contained in the crumb after dehydration using only a twin screw vent extruder, a relatively long L / D (screw length / screw diameter) is required. Even if the screw diameter per extrusion rate is increased and the productivity (sacrifice) is sacrificed, the quality of the block (smallness, transparency, etc.) required for applications such as sheets and films is satisfied. It was difficult to keep the concentration of the residual solvent in the polymer at 0.1% by mass or less, and it was difficult to say that the volatile component and the polymer were sufficiently separated.
[0004]
In addition, a method of removing water in crumbs by a drying device such as a screw extrusion type or kneader type dryer, an expander dryer, a hot air dryer, and the like (for example, see Patent Document 3) is known. After the wet crumb is completely dried, the dried crumb is supplied to an extruder to obtain a pellet-shaped block copolymer. Since there is no need for drying and desolvation in the extruder, there is an advantage that the size of the extruder is reduced.
However, in such a method, a large-sized hot-air dryer is used to dry and remove the moisture accompanying the crumb, and further to reduce the amount of the residual solvent in the block copolymer to a low level. Is required, the utility cost of steam, power, etc. is large, and there is a problem in terms of production efficiency. In addition, some of the crumb that has adhered to the dryer and stayed for a long time and deteriorated due to heat is mixed into the product, which often adversely affects the quality. Yes, poor productivity.
When a screw extrusion type or kneader type dryer is used, dehydration by pressing the crumb and removal of water by drying are relatively easy, but the amount of residual solvent in the crumb cannot be efficiently removed to a low level. Techniques for efficiently producing a block copolymer having a low final residual solvent concentration and satisfying the quality required for the use of a sheet, a film, and the like (there are few spots, transparency, etc.) have not yet been reported.
[0005]
[Patent Document 1]
JP-A-61-218614
[Patent Document 2]
JP-A-9-143222
[Patent Document 3]
JP-A-1-56713
[0006]
[Problems to be solved by the invention]
An object of the present invention is to obtain a crumb-shaped block copolymer by a steam stripping method, and to further dehydrate and remove the solvent to produce a block copolymer. It is an object of the present invention to provide a method for producing a block copolymer, which has a low residual solvent concentration and sufficiently satisfies the qualities required for applications such as sheets and films (there are few spots, transparency, etc.).
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to overcome the above-mentioned problems of the prior art, and as a result, steam-stripping a hydrocarbon solvent solution of a block copolymer composed of a vinyl aromatic hydrocarbon and a conjugated diene. After dehydrating the obtained crumb-shaped block copolymer, it is preliminarily dried with hot air at a temperature of 70 to 90 ° C., and then is subjected to a twin-screw extruder equipped with a deaeration slit and a devolatilization vent having a decompression means. By extruding, it has been found that a block copolymer having a low residual solvent concentration that satisfies the qualities required for applications such as a sheet and a film (there are few spots and transparency) and has a low residual solvent concentration.
[0008]
That is, the present invention is obtained by steam-stripping and dehydrating a solution of a block copolymer comprising a vinyl aromatic hydrocarbon and a conjugated diene polymerized in a hydrocarbon solvent using an organometallic compound as a catalyst. The crumb-like block copolymer is previously dried with hot air having a temperature of 70 to 95 ° C. so that the moisture content of the crumb is in the range of 5 to 20% by mass. Characterized by having at least one slit and at least one vent portion for devolatilization at a further downstream position thereof, wherein the vent portion is a twin-screw extruder having a decompression means and performs dehydration and desolvation. The present invention relates to a method for producing a block copolymer having a solvent concentration of 0.1% by mass or less.
[0009]
Here, the moisture content in the crumb after the preliminary drying is in the range of 5 to 20% by mass, preferably 5 to 15% by mass.
Since the crumb obtained by the steam stripping method is relatively porous, it is suitable to use a drying method by contact with hot air, for example, a flash drying method, etc. It has been newly found that drying can be easily performed and that the remaining solvent in the crumb can be efficiently removed by evaporation.
In the drying method using hot air, the hot air temperature is 70 to 95 ° C. If the hot air temperature exceeds 95 ° C., blocking of the polymer in the dryer tends to occur, and if the hot air temperature is lower than 70 ° C., efficient drying cannot be performed. As this preliminary drying method, a flash drying method using hot air is suitable because the moisture and residual solvent in the crumb can be efficiently removed by evaporation.
[0010]
If the water content after the pre-drying exceeds 20% by mass, drying and desolvation are carried out only by the extruder from crumbs having a large amount of water and residual solvent. It becomes difficult to secure the stability of the block copolymer (especially with few bumps and transparency) and to secure a low level of the residual solvent concentration by strengthening the shearing force. When the water content after the pre-drying is set to less than 5% by mass, a fluidized bed dryer, a heat conduction dryer or the like which can take a long residence time must be used. It is easy to get up and the equipment cost increases. In the predrying, there is also an effect of evaporating and removing the residual solvent in the crumb together with the evaporation and removal of the water in the crumb after dehydration, so that the next extrusion operation also has high productivity, few bumps, and good transparency. Further, it was found that a block copolymer having a low residual solvent concentration was obtained, and the present invention was completed based on this finding.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The method of the block copolymer used in the present invention is described, for example, in JP-B-36-19286, JP-B-43-17979, JP-B-48-2423, and JP-B-57-49567.
The polymer structure of the block copolymer used in the present invention is, for example,
(AB) n
(AB) nA
(BA) n-B
(Wherein, A represents a polymer block composed of a vinyl aromatic hydrocarbon, B represents a polymer block composed of a conjugated diene or a copolymer block composed of a vinyl aromatic hydrocarbon and a conjugated diene, and n is 1 The above is an integer, generally a block copolymer represented by an integer of 1 to 10.)
Or
[(AB) n] mx
[(BA) n] mX
[(AB) n-A] mX
[(BA) nB] mX
(Wherein A and B are as defined above, X represents a residue of a coupling agent such as silicon tetrachloride or tin tetrachloride, or a residue of an initiator such as a polyfunctional organolithium compound, n and m are integers of 1 or more, generally 1 to 10).
[0012]
In the present invention, as the vinyl aromatic hydrocarbon forming the block copolymer, for example, styrene, o- or p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methyl There are styrene, vinylnaphthalene, vinylanthracene, 1,1-diphenylethylene, and the like, and styrene is particularly commonly used. The vinyl aromatic hydrocarbons may be used alone or in combination of two or more.
Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. 3-butadiene, isoprene and the like. The conjugated diene may be used alone or in combination of two or more.
[0013]
Such a block copolymer can be produced by a known anionic polymerization method. A vinyl aromatic hydrocarbon and a conjugated diene are sequentially polymerized in a hydrocarbon solvent using an organolithium compound as a polymerization initiator to form a block copolymer. The polymerization time for producing the block copolymer may be any time required for the monomer to polymerize.
The polymerization temperature is generally between -10C and 160C, preferably between 40C and 140C. It is desirable to replace the atmosphere of the polymerization system with an inert gas such as nitrogen gas. The polymerization is carried out at a pressure sufficient to maintain the monomer and the solvent in a liquid phase within the above-mentioned polymerization temperature range. Care should be taken that impurities such as water, oxygen, carbon dioxide, etc., which inactivate the catalyst and the living polymer, are not mixed into the polymerization system. The weight average molecular weight of the block copolymer thus obtained is generally 5,000 to 1,000,000, preferably 10,000 to 500,000.
[0014]
When a random copolymer portion of a vinyl aromatic hydrocarbon and a conjugated diene is present in a polymer block mainly composed of a vinyl aromatic hydrocarbon or a polymer block mainly composed of a conjugated diene, The aromatic hydrocarbon may be uniformly distributed in the polymer block, or may be a tapered chain in which the ratio between the vinyl aromatic hydrocarbon and the conjugated diene changes continuously as the molecular weight increases. Further, in the copolymer portion, a plurality of portions in which vinyl aromatic hydrocarbon or conjugated diene is uniformly distributed and / or a plurality of portions in which taper shape is distributed may coexist.
[0015]
Examples of the hydrocarbon solvent include, for example, aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, and isooctane; cycloaliphatic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane; Examples thereof include aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene. These may be used alone or in combination of two or more.
[0016]
As the organometallic compound used as the polymerization initiator, an organolithium compound in which one or more lithium atoms are bonded in a molecule is generally used. For example, ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, hexamethylenedilithium, butadienyldilithium and the like. These may be used alone or in combination of two or more.
[0017]
In the polymerization, a randomizing agent can be used for adjusting the reactivity ratio between the vinyl aromatic hydrocarbon and the conjugated diene. As a randomizing agent, ethers such as dimethyl ether, diphenyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium and sodium Alkoxides.
[0018]
A crumb-like block copolymer can be obtained by steam stripping a solution of the block copolymer in a hydrocarbon solvent obtained by the above method or the like. The temperature of the liquid in the precipitation vessel where steam stripping is performed is set to be equal to or higher than the boiling point of the solvent, or equal to or higher than the azeotropic temperature when the solvent and water are azeotropic.
[0019]
In the steam stripping treatment, the concentration of the polymer in the hydrocarbon solvent solution of the block copolymer is adjusted to 5 to 60% by mass, preferably 10 to 50% by mass. It supplies to hot water in the state heated to 30-150 degreeC. The pressure in the precipitation can for forming crumbs by steam stripping is 0.05 to 0.15 MPa, preferably 0.10 to 0.12 MPa. When the pressure in the precipitation vessel is less than 0.05 MPa, the volume of generated steam increases, and foaming easily occurs in the precipitation vessel. When the pressure in the precipitation vessel exceeds 0.15 MPa, the temperature of the hot water in the precipitation vessel needs to be increased due to evaporation of the solvent. At this time, the aggregation of crumbs is likely to occur.
[0020]
In the above steam stripping, a surfactant may be added to hot water in a precipitation can or a desolvation can for the purpose of preventing agglomeration between crumbs, anionic surfactant, cationic surfactant, nonionic surfactant. Agents are commonly used. These surfactants are generally added in an amount of 0.0001 to 0.5% by mass relative to the water in the stripping zone. In addition to these surfactants, water-soluble salts of metals such as Li, Na, K, Mg, Ca, Al, and Zn can be used as a dispersing aid.
[0021]
In the above steam stripping method, a hydrocarbon solvent solution of the block copolymer is supplied into a liquid in a precipitation vessel having a stirrer and a baffle plate to form crumbs, and a slurry liquid in which crumbs are dispersed in water is obtained. I do.
[0022]
In addition, the slurry liquid containing crumb formed in the precipitation vessel is transferred to a desolvent vessel holding hot water at a temperature higher than the temperature in the precipitation vessel, and further steam stripping is performed to further remove the residual solvent in the crumb. Can be removed. In the desolvation can, as in the case of the precipitation can, stirring blades and baffles are provided in order to disperse the crumbs in water well, but the type and size of the stirring blades, the mounting position of the stirring blades, and the number of baffle plates There is no particular limitation on the stirring rotation speed and the like.
[0023]
The obtained slurry liquid is subjected to a dehydration treatment to obtain a wet crumb. Specifically, in the dehydration step, the slurry in a state in which crumbs are dispersed in water is dehydrated using a centrifugal dehydrator, a compression dehydrator, or the like, and a wet crumb is taken out. At this stage, the obtained water-containing crumb usually contains 20% by mass or more of water.
In order to reduce the water content in the crumb to 20% by mass or less only by the dewatering operation, it is necessary to perform dehydration for a long period of time. Absent.
[0024]
In the next drying step, the wet crumbs dehydrated by the above method are dried in advance using hot air at a temperature of 70 to 95 ° C. to reduce the water content in the crumbs to a range of 5 to 20% by mass, preferably 5 to 20% by mass. -15% by mass. Since the crumb obtained by the steam stripping method is relatively porous, it can be easily dried within the above-mentioned water range with an extremely short residence time, and at the same time, the remaining solvent can be efficiently removed by evaporation.
In the drying step, the solvent in the crumb after the dehydration is evaporated and removed, and the solvent remaining in the crumb has an effect of volatilization and removal. Therefore, in the next extrusion operation, the quality (there are few spots, transparency, etc.) is also reduced. A good block copolymer having a low residual solvent concentration can be obtained with high productivity.
[0025]
In order to pre-dry the crumb obtained by the steam stripping method and reduce the water content in the crumb to 20% by mass or less or 15% by mass or less, hot air capable of efficiently evaporating and removing the residual solvent simultaneously with the moisture in a short residence time. Is suitable, but not particularly limited thereto.
Usually, in order to carry out pneumatic transport of the dehydrated crumb obtained by the above method to the supply hopper of the extruder, by heating the crumb transport air, the airflow type drying equipment that also serves as pneumatic transport is used for preliminary drying. It can be used, does not require large drying equipment, requires very short residence time, and solves the problem of thermal degradation of quality.
[0026]
In the next extrusion operation, a crumb having a low residual solvent concentration, a small number of bumps, and a good transparency is used in a relatively small twin-screw extruder in order to handle crumbs which are previously dried and have a small amount of water and residual solvent. It was found that the copolymer could be obtained with high production efficiency. In the case where the dehydrated crumb is directly dewatered, dried and solvent-removed by a twin-screw extruder without drying in advance, the screw diameter per polymer extruded amount is increased, and the L / D (screw) of the extruder is increased. Length / screw diameter), a strong shear force is required, and it is difficult to keep the amount of residual solvent at a low level after stably ensuring product quality (less bumps, transparency, etc.). Become.
[0027]
Therefore, a crumb-shaped block copolymer obtained by drying in advance by the above-described method is charged from a supply hopper, and at least one slit for deaeration positioned downstream of the block hopper and further devolatilized at a position downstream thereof. And at least one vent portion, and the vent portion is a twin-screw extruder having a decompression means, and performs dehydration and solvent removal. Since the crumb-shaped block copolymer supplied from the supply hopper contains water and a residual solvent, when the temperature near the supply port from the supply hopper rises, blocking easily occurs near the supply port, making it difficult to continue operation. . As a countermeasure, a slit for deaeration is provided downstream of the feed hopper, and water vapor generated in the extruder is extracted from the slit for deaeration to prevent a rise in temperature near the inlet from the supply hopper. The stable supply of the polymer to the extruder became possible. The water contained in the block copolymer supplied to the twin-screw extruder is extracted from a devolatilizing vent provided with a deaeration slit and a decompression means, and most of the residual solvent is devolatilized using a decompression means. Is extracted as steam from the vent part of
[0028]
In the twin-screw extruder, at least one deaeration slit, at least one dewatering slit, and at least one devolatilization vent are provided downstream of the feed hopper. You can also. The squeezing in the twin-screw extruder is strengthened, and water is squeezed out from the slit for dewatering, and the remaining moisture is removed as steam from the slit for deaeration and the vent for devolatilization downstream thereof.
[0029]
In the above-mentioned twin screw extruder, one having an L / D (screw length / screw diameter) of about 20 to 60 can be used. The temperature of the block copolymer at the deaeration or dewatering slit located downstream from the feed hopper to the twin-screw extruder is preferably 60 ° C. or less, and the vent portion located further downstream is preferably 100 mmHg or less. Preferably, the pressure is reduced to 50 mmHg or less, the block copolymer is extruded at 250 ° C or less, and cut with a cutter to obtain a pellet-shaped block copolymer having a residual solvent concentration of 0.1% by mass or less.
[0030]
When two or more devolatilizing vents are provided and each vent is operated at a different degree of reduced pressure, it is preferable that a sealing member is provided on the screw between each vent. The sealing member is generally formed of a screw member having a reverse rotation, but may be a kneading disk having a structure in which a plurality of disks having no ability to transport a polymer are laminated. As for the screw engagement mechanism, an engagement type having a self-cleaning property is preferable. The rotation directions of the two screws may be different directions or the same direction.
[0031]
The residual solvent amount of the pellet-shaped block copolymer obtained in the present invention is preferably 0.1% by mass or less, more preferably 0.05% by mass or less. The resin temperature in the twin-screw extruder is preferably from 150 to 250C, more preferably from 180 to 230C. If the temperature of the block copolymer exceeds 250 ° C., the breaking and crosslinking of the polymer molecular chain will occur significantly, which is not preferable.
[0032]
The crumb-shaped block copolymer and another resin can be blended in a supply hopper, supplied to such an extruder, and compounded. The crumb-shaped block copolymer may be supplied from a supply hopper, and another resin may be supplied from the middle of the twin-screw extruder to be compounded.
[0033]
Various additives can be added to the block copolymer obtained in the present invention as needed. In order to cope with the case where the block copolymer is subjected to various heat treatments or the molded product is used under an oxidizing atmosphere or irradiation of ultraviolet rays, etc., the physical properties are deteriorated, and the physical properties suitable for the intended use are also adjusted. For further imparting, additives such as stabilizers, lubricants, processing aids, antistatic agents, antiblocking agents, weathering agents, softeners, lubricants, weathering agents, and coloring agents can be used. These additives can be added in any step after the completion of the polymerization reaction. For example, it may be mixed with the block copolymer solution after the polymerization, may be mixed in the middle or at the tip of the twin-screw extruder, or may be added at a plurality of locations.
[0034]
Examples of the stabilizer used to prevent oxidative deterioration and thermal deterioration of the block copolymer during steam stripping, drying and extrusion are, 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-methyl Phenolic antioxidants such as phenyl acrylate, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, and 2,6-di-tert-butyl-4-methylphenol; 2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, trisnonylphenyl phenyl And phosphoric acid-based antioxidants such as bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol-diphosphite, etc. These stabilizers may be used after polymerization. It can be added in such a step, and it is generally desirable to use it in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of the block copolymer.
[0035]
Next, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited to these examples. The method for producing the block copolymer used in the examples and comparative examples is described below.
Embodiment 1
(Polymerization operation)
[Block copolymer (A)]
Under a nitrogen gas atmosphere, 0.18 parts by mass of n-butyllithium was added to 257 parts of cyclohexane, 22 parts by mass of styrene was added, and polymerization was carried out at 55 ° C. for 20 minutes. Then, 45 parts by mass of butadiene, and then styrene 33 parts by mass were added and polymerization was carried out at 120 ° C. for 110 minutes. A cyclohexane solution of the block copolymer having a styrene content of 55% by mass was obtained. The concentration of the block copolymer dissolved in the cyclohexane solvent was 28% by mass.
[Block copolymer (B)]
Under a nitrogen gas atmosphere, 0.07 parts by mass of n-butyllithium was added to 223 parts of cyclohexane, 34 parts by mass of styrene was added, polymerization was carried out at 65 ° C. for 20 minutes, and 12 parts by mass of butadiene were added. Polymerized for minutes. Thereafter, 3 parts by mass of butadiene and 51 parts by mass of styrene were added, and polymerization was carried out at 100 ° C. for 80 minutes. A cyclohexane solution of the block copolymer having a styrene content of 85% by mass was obtained. The concentration of the block copolymer dissolved in the cyclohexane solvent was 31% by mass.
[0036]
(Steam stripping operation)
33 parts by mass of the solution of the block copolymer (A) and 67 parts by mass of the solution of the block copolymer (B) were stirred and mixed. The block copolymer solution was subjected to steam stripping to obtain a slurry containing crumb. A stainless steel can having an internal volume of 1000 liters was used as a deposition can for performing steam stripping. The block copolymer solution was supplied to the precipitation vessel at a rate of 141 kg / hour, water at 30 ° C. was supplied at a rate of 1200 L / hour, and steam stripping was performed. The temperature of the supplied block copolymer solution was 50 ° C. As a crumb dispersant, a block polymer of polyoxyethylene and polyoxypropylene having an average molecular weight of 4900 and an ethyleneoxyethylene content of 30% by mass was used in an amount of 2000 ppm with respect to water in the stripping zone. Steam was continuously fed into the precipitation vessel so that the temperature of the hot water in the precipitation vessel was 85 ° C., and was precipitated as crumbs dispersed in the hot water. The precipitation can was provided with four paddle blades and four plate baffles, and the crumbs were stirred and mixed in hot water to be dispersed. The pressure in the gas phase inside the precipitation vessel was 0.110 MPa.
[0037]
(Dehydration and drying operations)
The slurry liquid containing crumb obtained by steam stripping was supplied to a centrifugal dehydrator, and the wet crumb was taken out and dried in advance with a flash dryer. The hot air introduced into the flash dryer was heated by a heater so that the temperature became 80 ° C. The exhaust air temperature of the flash dryer was 50 to 55 ° C, and the average crumb residence time in the dryer was 2 seconds. According to JIS-K-6383, the moisture content of the crumb dried by this method was dried at 105 ° C. ± 5 ° C. for 1 hour, then cooled in a desiccator, and the difference in mass before and after drying was defined as the moisture content. (Water content) / (water content + block copolymer after drying) was calculated in percentage. The residual cyclohexane concentration in the crumb was analyzed by gas chromatography. The crumb obtained by the above method had a water content of 15% by mass and a residual cyclohexane concentration of 0.7% by mass.
[0038]
(Extrusion operation)
As a twin-screw extruder, one deaeration slit and two vents for devolatilization are provided downstream of the slit, and the vent portion has a decompression means, and has a screw outer diameter of 59 mm and L / D = 40. A two-way extruder was used. The crumb containing water of 15% by mass was previously dehydrated and dried, and was continuously supplied from the supply hopper to the twin-screw extruder at a rate of 318 kg / Hr. The polymer throughput was 270 kg / Hr. 0.5 parts by weight of 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl-4-methylphenylacrylate) as a stabilizer was added to 100 parts by weight of the supplied polymer by a weight feeder. The screw was continuously supplied to the hopper for supplying the crumb at 450 rpm as the operating conditions, and the pressure of each vent portion for devolatilization was 60 mmHg (No. 1 vent portion), 50 mmHg (second vent portion) The degassing slit barrel was not heated, and the barrel of each vent portion downstream thereof was set at 200 ° C. The temperature of the degassing slit barrel was indicated at 27 ° C. However, the barrel temperature of the first vent located downstream thereof was 198 ° C, and the barrel temperature of the second vent was 201 ° C. Was fitted with a 325 mesh screen, and the resin temperature at the die outlet was measured to be 243 ° C. The polymer coming out of the die hole in the form of a strand was cooled in a water bath, and then cut into a length of about 3 mm with a pelletizer. The pellets were obtained, and the operating conditions and measurement results are shown in Table 1.
[0039]
(Measure)
The residual cyclohexane concentration in the pelletized block copolymer obtained by the above method was measured by the above method, and is shown in Table 1. Further, 50 g of the pellet was dissolved in 200 g of toluene, suction-filtered with a filter paper having a diameter of 70 mm (thickness: 0.22 mm, supplementary particle diameter: 7 μm, collection efficiency: 75%), and then captured on the filter paper with violet 36. The gel component in the pellet was stained 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 to 10 small gels
3: 0 large gels, 3 to 5 medium gels, 3 to 10 small gels, or 0 large gels, 2 or less medium gels, 11 to 20 small gels
4: 0 large gel, 6 to 10 medium gels, 3 to 10 small gels, or 0 large gels, 3 to 5 medium gels, 11 to 20 small gels, or 0 large gels, 2 medium gels 21 or less small gels, 1 to 2 large gels, 1 to 2 large gels, 2 or less medium gels, 20 or less small gels
5: Gel grades other than 1-4
Here, a large gel refers to one having a diameter of 0.5 mm or more, a medium gel refers to a diameter of 0.2 mm to less than 0.5 mm, and a small gel refers to one having a diameter of less than 0.2 mm.
[0040]
The operating conditions, operating conditions and measurement results (moisture content of the supplied crumb, residual cyclohexane concentration and residual cyclohexane concentration in the obtained pellet-shaped block copolymer, gel grade) of each Example and each Comparative Example shown below are shown. The results are shown in Tables 1 and 2.
[0041]
[Examples 2 and 3]
Example 2 was performed in the same manner as in Example 1 except that the screw rotation speed was set to 400 rotations / minute. Example 3 was performed in the same manner as in Example 1 except that the screw rotation speed was 550 rotations / minute. The results are shown in Table 1.
[0042]
Embodiment 4
Example 4 was performed in the same manner as in Example 1 except that a dewatering slit was provided behind the deaeration slit. The deaerated slit barrel and the dewatered slit barrel were not heated. The results are shown in Table 1.
[0043]
[Comparative Example 1]
Comparative Example 1 was carried out in the same manner as in Example 1 except that dewatered crumbs not previously subjected to a drying treatment were supplied to a twin-screw extruder. Some scattering of the polymer was observed from the devolatilization vent. The results are shown in Table 2.
[0044]
[Comparative Examples 2-3]
Comparative Example 2 was carried out in the same manner as in Example 1 except that dewatered crumbs not previously subjected to drying treatment were supplied to a twin-screw extruder, and the screw rotation speed of the twin-screw extruder was set to 550 rpm. Comparative Example 3 was carried out in the same manner as in Example 1 except that dewatered crumbs not previously subjected to a drying treatment were supplied to a twin-screw extruder and the screw rotation speed was set to 630 rotations / minute. The results are shown in Table 2.
[0045]
[Comparative Examples 4 and 5]
In Comparative Example 4, the dewatered crumb not previously subjected to the drying treatment was supplied to the twin-screw extruder, and the wet crumb was supplied such that the amount of polymer extruded by the twin-screw extruder was 210 Kg / Hr. Performed in the same manner as in Example 1. Comparative Example 5 was performed in the same manner as in Example 1 except that the dewatered crumb not previously subjected to the drying treatment was supplied to the twin-screw extruder, and the crumb in a wet state was supplied so that the polymer extrusion amount was 160 kg / Hr. went. The results are shown in Table 2.
[0046]
[Comparative Example 6]
Comparative Example 6 was carried out except that the dewatered crumbs which had not been subjected to the drying treatment beforehand were supplied to the twin-screw extruder, and the pressure of each vent portion of the twin-screw extruder was set to 45 mmHg and 35 mmHg in order from the crumb supply port side. Performed as in Example 3.
[0047]
[Comparative Example 7]
Comparative Example 7 was performed in the same manner as in Example 1 except that the twin-screw extruder was extruded without providing a slit for deaeration and a slit for dehydration. Crumb was blocked near the crumb supply port, and the operation could not be performed and the pellet could not be collected.
[0048]
[Comparative Example 8]
Comparative Example 8 was carried out in the same manner as in Example 1 except that the twin-screw extruder was not provided with a slit for deaeration, and was provided with only a slit for dewatering and was extruded. Crumb was blocked near the crumb supply port, and the operation could not be performed and the pellet could not be collected.
[0049]
[Table 1]

[0050]
[Table 2]

[0051]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, after performing moderate dehydration and drying beforehand, it supplies to a twin-screw extruder and performs dehydration and desolvation, and can obtain the block copolymer with a small residual solvent amount efficiently. A method is provided. The resulting block copolymer has few bumps and is excellent in transparency and color tone, so it can be used for sheets, films, injection molded products of various shapes, vacuum molded products, compressed air molded products, or industrial parts, household goods, toys, etc. It can also be used as a material. In particular, the block copolymer obtained in the present invention has a low residual solvent amount, is excellent in transparency, and has a low gel content, so that it is used for medical supplies, food containers, food packaging materials, labels for beverage bottles and the like. It is valid.
[0052]
[Brief description of the drawings]
FIG. 1 is a process schematic diagram for explaining claim 1 of the present invention.
FIG. 2 is a process schematic diagram for explaining claim 2 of the present invention.
[Explanation of symbols]
1: Extruder
2: Supply hopper
3: Twin screw
4: Slit for deaeration
5; vent part
6; die
7; slit for dewatering

Claims (3)

A clam-like block obtained by steam-stripping the solvent from a solution of a block copolymer consisting of a vinyl aromatic hydrocarbon and a conjugated diene, which was polymerized using an organometallic compound as a catalyst in a hydrocarbon solvent, and dehydrated. The copolymer is dried in advance with hot air at a temperature of 70 to 95 ° C. to a moisture content of 5 to 20% by mass, then charged from a supply hopper, and at least one deaeration slit located downstream thereof and further downstream thereof. A block having a residual solvent concentration of 0.1% by mass or less, wherein at least one vent portion for devolatilization is provided at a position, and the vent portion is a twin-screw extruder having a decompression means for performing dehydration and desolvation. A method for producing a copolymer. Downstream of the supply hopper according to claim 1, at least one slit for deaeration, at least one slit for dehydration and at least one vent portion for devolatilization at a position further downstream thereof, The method for producing a block copolymer having a residual solvent concentration of 0.1% by mass or less according to claim 1, wherein dehydration and desolvation are performed by a twin-screw extruder having a decompression means. 3. The method according to claim 1, wherein the temperature of the block copolymer at the deaeration or dewatering slit located downstream from the supply hopper is 60 ° C. or less, and the vent located further downstream is 100 mmHg. A method for producing a pellet-like block copolymer having a residual solvent concentration of 0.1% by mass or less, obtained by extruding the block copolymer at 250 ° C. or less under reduced pressure and cutting with a cutter.

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