JPS6160084B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for producing a copolymer of a conjugated diene and maleic anhydride, which is a hydrolyzed copolymer purified from a copolymerization reaction product of a conjugated diene and maleic anhydride. The present invention relates to a method for recovering a concentrate in high yield and with good purity. It is well known that when a conjugated diene and maleic anhydride are reacted in the presence of a radical initiator or ionizing radiation, they copolymerize to form a so-called alternating copolymer in which the conjugated diene and maleic anhydride are alternately bonded. ing. Utilizing its excellent adhesive properties, this alternating copolymer is being developed for various uses such as adhesives and impregnating agents for textiles and leather. Derivatives of this alternating copolymer, especially water-soluble salts, are used in various applications such as adhesives, dyeing aids, and paper sizing agents. In order to obtain a water-soluble salt of a conjugated diene-maleic anhydride copolymer, that is, a salt of a conjugated diene-maleic anhydride copolymer, an alternating copolymer obtained by a copolymerization reaction of a conjugated diene and maleic anhydride is generally used. A method is used in which the compound is reacted with a base such as sodium hydroxide or ammonium hydroxide in water. By the way, in the copolymerization reaction of conjugated diene and maleic anhydride, the conjugated diene and maleic anhydride
Diels-Alder reaction occurs, resulting in tetrahydrophthalic anhydride or substituted tetrahydrophthalic anhydride (hereinafter abbreviated as THPA in the present invention)
It is well known that it is a by-product. In addition, in the copolymerization reaction of conjugated diene and maleic anhydride,
Good solvents for copolymers (e.g. cyclohexanone,
It is well known that if polar solvents such as acetone, dioxane, tetrahydrofuran, and dimethyl sulfoxide are not used as the polymerization solvent, the resulting copolymer will gel during the copolymerization reaction and lose its commercial value. . That is, in order to obtain a water-soluble salt of a conjugated diene-maleic anhydride copolymer, first, each monomer component is copolymerized using a good solvent for the copolymer to synthesize a copolymer, and then a copolymer is synthesized in a polymerization solution. THPA by-produced from
It is necessary to recover a highly pure copolymer that does not contain any of the following, and then to react the recovered copolymer with a predetermined base in water. As a method for recovering the copolymer, a conventional method for recovering the polymer from the polymerization reaction mixture (for example, a method in which steam is blown into the polymerization solution and the solvent is steam-stripped to recover the polymer) was replaced with a butadiene-maleic anhydride copolymer. Application to polymerization solutions containing polymers is unsuitable because THPA cannot be completely removed. In addition, as a method for recovering the conjugated diene-maleic anhydride copolymer from the copolymerization reaction mixture (copolymerization reaction solution), a good solvent for THPA and a poor solvent for the copolymer (substantially no copolymer A large amount of a solvent that cannot be dissolved in the precipitant (e.g., aromatic hydrocarbons such as benzene, toluene, xylene, or halogenated hydrocarbons such as methylene chloride, chloroform, etc.) is used as a precipitant, and the copolymerization reaction is carried out in this precipitant. Gradually add the mixture to precipitate the copolymer into powder or lumps while adding THPA.
A method has been adopted in which the substance is dissolved in a precipitant. This copolymer recovery method certainly has the advantage of being able to remove THPA, but on the other hand, it requires the use of an extremely large amount of precipitation solvent to separate and recover a small amount of copolymer. A major drawback of this method was that the recovery and purification of the precipitation solvent were too costly. In order to improve the drawbacks of the above-mentioned recovery methods for recovering purified copolymers from copolymerization reaction mixtures, water is added to the copolymerization reaction mixture, the mixture is heated, and the solvent is distilled off by steaming to remove the remaining residue. A method has been proposed in which the purified copolymer is recovered by cooling the mixture and separating it into a lower layer containing the copolymer and an upper layer containing the by-product THPA.
29725). However, this method has drawbacks such as an insufficient removal rate of by-product THPA and a not so high recovery rate of the conjugated diene-maleic anhydride copolymer. As a result of intensive research by the present inventors in order to solve the drawbacks of the method of recovering a copolymer from the copolymerization reaction product of these conjugated dienes and maleic anhydride,
A method of recovering a purified copolymer by adding a predetermined amount of recovery solvent to a copolymerization reaction solution and separating the liquid into a solution containing a concentrated copolymer and a solution containing polymerization byproducts. I have already proposed this (patent application 115130/1986). This method is an excellent method for easily recovering a highly pure conjugated diene-maleic anhydride copolymer from a copolymerization reaction solution, but if the objective is to obtain a water-soluble salt of the copolymer, it may be necessary to further prepare a base. A reaction step is required. Special application 1977-
In the method of 115130, the purified copolymer is obtained as a highly concentrated and highly viscous solution, so the remaining solvent is removed and the dried copolymer is reacted with a base in water to obtain a water-soluble copolymer salt. Alternatively, water is added to a highly concentrated copolymer solution that still contains the solvent to hydrolyze it, gradually replacing the water and solvent (the solvent is distilled off), and after the solvent has been distilled off. There are two ways to obtain a water-soluble salt by adding a base such as sodium hydroxide. However, the drying process in the former method is expensive, and the conjugated diene maleic anhydride copolymer is extremely sticky if it contains even a small amount of solvent (especially a good solvent for the copolymer). impractical. On the other hand, even in the latter method, after the purified copolymer is once separated, a further hydrolysis operation is added, which makes the operation complicated. The present inventors have developed a method for recovering a copolymer from a copolymerization reaction solution containing a conjugated diene-maleic anhydride copolymer. The present invention was achieved as a result of efforts to develop a recovery method suitable for cases where the purpose is to synthesize chemical salts. That is, in the present invention, when a conjugated diene and maleic anhydride are solution copolymerized using a polymerization solvent, and a conjugated diene-maleic anhydride copolymer is recovered from the copolymerization reaction solution, the copolymerization reaction solution is used for the reaction. The copolymer and by-products are hydrolyzed by adding an equimolar to 10 times the molar amount of water to the maleic anhydride, and then 0.05 to 2 parts of water is added to each part of the polymerization solvent in the copolymerization reaction solution. In the invention, parts represent parts by weight. A solution containing a concentrated hydrolyzed copolymer and a solution containing hydrolyzed by-products are obtained by adding and mixing a recovery solvent that does not dissolve the hydrolyzed copolymer and is compatible with the polymerization solvent. The present invention relates to a method for recovering a conjugated diene-maleic anhydride copolymer, which comprises recovering the conjugated diene-maleic anhydride copolymer as a hydrolyzed purified copolymer by liquid-liquid separation. According to the method of the present invention, when recovering a copolymer from a copolymerization reaction solution, a highly purified hydrolyzed copolymer can be obtained, which is advantageous for synthesizing a water-soluble salt of the copolymer. Not only that, the removal rate of by-product THPA is very high, and the removal of polymerization catalyst residue is also easy. The conjugated diene referred to in the present invention usually has 4 to 12 carbon atoms.
butadiene, isoprene, piperylene, 2-chloro-1,3-butadiene, 2,3
-dichloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 1-methoxy-1,
A typical example is 3-butadiene. Furthermore, the polymerization solvent referred to in the present invention is one that dissolves the copolymer to be produced, and therefore the polymerization reaction is solution polymerization. Examples of the polymerization solvent include cyclohexanone, acetone, dioxane, tetrahydrofuran, and dimethyl sulfoxide. In the polymerization reaction, the molar ratio of conjugated diene to maleic anhydride is usually in the range of 1:0.5 to 1.5, and the polymerization solvent can be used in an amount of usually 2 to 10 times the weight of the monomer. Although various catalysts can be used for the polymerization reaction, polymerization using a radical initiator and ionizing radiation is typical. Although the polymerization temperature is not particularly limited, it is generally carried out at 30 to 100°C. By such polymerization, a polymerization reaction solution (polymerization reaction mixture) having a copolymer concentration of usually 7 to 40% by weight, preferably 10 to 25% by weight is obtained. The present invention relates to recovering a copolymer from this polymerization reaction solution, and particularly relates to a method for recovering the copolymer as a hydrolyzed copolymer.
The term "hydrolyzed copolymer" as used herein means a copolymer in which all the maleic anhydride units in the copolymer react with one molecule of water to open the ring and become maleic acid units. The amount of water used to convert maleic anhydride units in the copolymer into maleic acid units is from equimolar to 10 times the molar amount of the maleic anhydride monomer used for polymerization. . As mentioned above, THPA is produced as a by-product in this polymerization reaction, and THPA
reacts with water and similarly opens the ring to form tetrahydrophthalic acid (substituted tetrahydrophthalic acid). Further, depending on the polymerization conditions, the charged maleic anhydride may remain unreacted, and this reacts with water to form maleic acid. Therefore, since THPA or both THPA and maleic anhydride coexist in the polymerization solution, a portion of the added water reacts with THPA or THPA and maleic anhydride and is consumed. Therefore, in order to completely hydrolyze the copolymer in the polymerization solution, a minimum equimolar amount of water is required relative to the maleic anhydride used in the polymerization. In addition, if a large excess of water is used, the separation efficiency will be reduced when the recovery solvent is added to separate the copolymer-rich layer and the by-product rich layer (the by-product content in the copolymer will increase). To increase). Therefore, it is not preferable to use more than 10 times the molar amount of water. The rate at which water is added to the polymerization solution depends on the amount of water used, but is generally preferably 30 minutes to 3 hours. If the addition rate is too fast, the unhydrolyzed copolymer will precipitate in a sticky, difficult-to-handle state. Also, it is pointless to add water for too long, and in that sense 30 minutes to 5 hours is appropriate. Also, the appropriate temperature for adding water is 20°C to 100°C, and generally the speed of water addition can be increased by heating the polymerization solution and adding water while stirring thoroughly, but the temperature at 20°C to 30°C is Hydrolysis can be carried out even at room temperature. The polymerization solvents used are mostly polar solvents and are compatible with water, so the hydrolysis reaction is often carried out in a homogeneous system.However, for example, cyclohexanone can be used as a polymerization solvent because it is a good solvent for copolymers. However, some have low compatibility with water. However, the amount of water added is small relative to the polymerization solvent, and even if water is added above the solubility limit of water in the solvent, hydrolysis can be completed if sufficient stirring and sufficient time are used. be exposed. The state of the polymerization solution after hydrolysis is thus completed varies depending on the type of polymerization solvent used. For example, when dimethyl sulfoxide is used, it remains a homogeneous solution even after hydrolysis, and even when acetone is used, it often remains a homogeneous solution, although this varies depending on the amount of water. On the other hand, in the case of cyclohexanone, methyl ethyl ketone, etc., a layer rich in already hydrolyzed copolymers often separates at this point. In the former case of a homogeneous solution, of course, THPA has not been separated yet, and even in the latter case, the separation of the copolymer and by-products such as THPA is incomplete. In order to achieve complete separation in the method of the present invention, a recovered solvent is then added to the polymerization solution. The recovery solvent used in the present invention is a solvent that cannot substantially dissolve the hydrolyzed conjugated diene-maleic anhydride copolymer in the temperature range from room temperature to 100°C, and is compatible with the polymerization solvent. For example, aliphatic hydrocarbons such as n-butane, i-butane, n-pentane, iso-pentane, n-hexane, iso-hexane, n-heptane, iso-heptane, n-octane, or cyclopentane. , alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene, toluene, xylene, halogenated aliphatic hydrocarbons or halogenated aromatic hydrocarbons such as methylene chloride, chloroform, chlorobenzene, ethyl acetate, butyl acetate. , aliphatic or aromatic ester compounds such as ethyl benzoate. Of course, it is also possible to use a mixture of one or more of these recovered solvents. The amount of recovered solvent to be added to the copolymerization reaction solution after addition of water in the present invention naturally depends on the composition of the copolymerization reaction solution, but generally it is 1 part of the polymerization solvent in the copolymerization reaction product. The range is from 0.05 to 2 parts, preferably from 0.1 to 1.0 parts.
If the amount of recovery solvent used is small, the recovery rate of the hydrolyzed copolymer will be low, and if too much recovery solvent is added, the recovery rate of the hydrolyzed copolymer will be high, but the solution layer containing a large amount of copolymer will Due to the increased viscosity, handling becomes difficult and the polymer cannot be effectively recovered.
There are no particular restrictions on the method of mixing and adding the recovered solvent to the copolymerization reaction solution, for example, adding the recovered solvent to the copolymerization reaction solution for 10 minutes to 5 minutes while stirring the solution thoroughly.
It may be added little by little over a period of time, or in some cases, the recovered solution may be added almost instantaneously while stirring the copolymerization reaction solution well. There is no particular limit to the temperature of the copolymerization reaction solution when adding the recovered solvent; for example, from 0°C to
It is possible to carry out in the temperature range of 100°C. After adding the recovered solvent to the copolymerization reaction solution after water addition, the mixture is heated at a temperature range of usually 0°C to 200°C, preferably 10°C to 150°C for 10 minutes to 40 minutes.
Stirring is carried out for a period of time, preferably 30 to 20 hours, to reach a distribution equilibrium between a solution layer (or droplets) rich in the hydrolyzed copolymer and a solution layer (or droplets) rich in the hydrolyzate of by-product THPA. It is desirable to If the operation at this stage is not carried out sufficiently, the copolymer recovery rate may be insufficient, or impurities such as by-product THPA or catalyst residue may not be sufficiently removed. Of course, the time required for this stirring depends on the stirring method, but it is desirable to adopt a stirring method that reaches distribution equilibrium in as short a time as possible. This mixture is then separated into two liquid-liquid layers. Layer separation is usually achieved by standing. In the present invention, in this liquid-liquid separation, a solution containing a hydrolyzed copolymer that is more concentrated than the copolymer concentration in the initial copolymerization reaction solution is obtained, and a solution containing by-product THPA is obtained on the other hand. It is characterized by the fact that a solution rich in hydrolysates of is obtained. Generally, the hydrolyzed copolymer-rich solution is in the lower layer;
A solution rich in the hydrolyzate of by-product THPA becomes the upper layer, but if a solvent with a high specific gravity such as chloroform is used as the recovery solvent, a solution rich in copolymer becomes the upper layer. In any case, it is necessary to allow these mixtures to stand for a sufficient period of time to allow them to be separated. The time required for static separation of the mixture depends on the shape of the container used for static separation and the degree of agitation of the mixture, but generally it can be carried out within 10 minutes to 24 hours. be. In addition to static separation, the mixture may be separated by a liquid-liquid separation method used in the general chemical industry, such as a centrifugal separation method. The hydrolyzed copolymer can be separated from the copolymer-rich solution that has been hydrolyzed, recovered, and purified from the copolymerization reaction solution by the method of the present invention, for example, by drying this solution as it is to remove the solvent. It is also possible to precipitate and recover the hydrolyzed copolymer by adding it to a solvent that does not dissolve the hydrolyzed copolymer. When the copolymer is recovered by the latter method, the copolymer concentration is high, so there is an advantage that the amount of recovery solvent used can be extremely small. Furthermore, the characteristics of the present invention are best exhibited when a water-soluble copolymer salt is synthesized from a solution rich in the hydrolyzed copolymer obtained by the present invention. That is, in the present invention, since the copolymer has already been hydrolyzed, it easily dissolves in hot water. Therefore, an appropriate amount of water is added to a solution rich in the hydrolyzed copolymer while heating, and the solvent originally contained in the solution is removed by distillation or steam stripping. An aqueous solution of is obtained. Then, by adding a predetermined amount of a base such as sodium hydroxide or ammonium hydroxide or an aqueous solution thereof, a water-soluble salt of the conjugated diene-maleic anhydride copolymer can be easily synthesized. It is very advantageous that all these operations can be performed uniformly and continuously. Separation and recovery of the copolymer of the present invention can be carried out batchwise, but for greater economy, it can also be carried out semi-batchwise or continuously. Furthermore, by repeating the copolymer recovery method of the present invention twice or more, it is possible to further reduce the impurity content in the recovered copolymer. In order to further improve the purity of the copolymer by repeating the method of the present invention twice or more, it is possible to separate and
To the recovered hydrolyzed copolymer-rich solution, a solvent that dissolves the hydrolyzed copolymer (such as dimethyl sulfoxide, dimethyl formazide, acetone, and an acetone/water mixed solvent) is added to the initial solution. This can be carried out by preparing a solution with a composition ratio close to that of the copolymer and polymerization solvent in the copolymerization solution, and then adding the recovered solvent according to the method of the present invention. In the second separation operation, since the copolymer has already been hydrolyzed, the step of adding water can be omitted. As mentioned above, the method of the present invention has a high recovery rate of the copolymer (hydrolyzed copolymer) from the copolymerization reaction product, a high removal rate of by-product THPA, and a high removal rate of catalyst residue. Moreover, it is an extremely simple and economical method for recovering copolymers, and is extremely advantageous when synthesizing water-soluble salts of copolymers. The features of the present invention will be explained in more detail with reference to Examples below. Example 1 98.1 g (1.0 mol) of maleic anhydride, 1.6 g of azobisisobutyronitrile and 750 g of acetone were placed in a nitrogen-substituted autoclave and heated to 70°C. 54.1 g (1.0 mol) of butadiene was charged into this solution over 3 hours. After the butadiene charging was completed, the reaction was continued for 1 hour at the same temperature and then cooled. Next, transfer the polymerization solution to the second separable flask.
36g (2.0mol) of water while heating to 50℃ and stirring
was added dropwise over 2 hours to hydrolyze the copolymer and THPA. Next, 225 g of n-hexane (i.e., 0.3 parts per part of acetone as the polymerization solvent) was added over 2 hours under the same conditions, stirring was continued for another 2 hours, and then left to stand for 15 hours. It separated into an upper layer and a pale yellow viscous lower layer. The tetrahydrophthalic acid content and the butadiene-maleic acid copolymer content in the upper and lower layers were respectively determined by gas chromatography and a polymer precipitation fractionation method using ethyl acetate as a precipitant, and the results shown in Table 1 were obtained. Furthermore, when the IR spectrum of the copolymer obtained by the polymer precipitation method was measured, absorption based on maleic anhydride units completely disappeared, and absorption based on maleic acid units was observed instead. Example 2 98.1 g (1.0 mol) of maleic anhydride, 2.4 g of benzoyl peroxide, and 750 g of cyclohexanone were placed in a nitrogen-substituted autoclave No. 2.
Heated to 70°C. 54.1g of butadiene in this solution
(1.0 mol) was added over 2 hours. After the butadiene charging was completed, the reaction was continued for an additional hour. Next, add 27 g (1.5 mol) of water while keeping the temperature at 70°C.
It took 30 minutes to prepare and continued stirring for 3 hours. Then, 300 g of benzene was added over 3 hours while stirring well, and the mixture was stirred for another hour. 5
After standing still for a period of time, the autoclave contents were separated into a low viscosity upper layer colored reddish brown due to catalyst residue and a pale yellow high viscosity lower layer containing almost no catalyst residue. The upper and lower layers were analyzed in the same manner as in Example 1, and the results shown in Table 1 were obtained. Furthermore, IR spectrum measurements revealed that the copolymer was completely hydrolyzed. Example 3 A polymerization solution synthesized in the same manner as in Example 1 was treated in the same manner as in Example 1 to separate a pale yellow viscous lower layer, which was diluted by adding 400 g of acetone. Next, this liquid was transferred to a separable flask (No. 2) and stirred while heating to 50° C., 150 g of n-hexane was added over 2 hours, and stirring was continued for an additional 2 hours. When the components in the upper and lower layers of the obtained two-layer separated liquid, which was allowed to stand still for 15 hours after the stirring was completed, were analyzed in the same manner as in Example 1, as shown in Table 1, it was found that the amount of butadiene was even higher than that in Example 1. The maleic acid copolymer and tetrahydrophthalic acid were well separated. Example 4 98.1 g (1.0 mol) of maleic anhydride, 1.6 g of azobisisobutyronitrile and 500 g of tetrahydrofuran were placed in a nitrogen-substituted autoclave and heated to 80°C. Butadiene 54.1 in this solution
g (1.0 mol) was added over 1 hour. After the butadiene charging was completed, the reaction was continued for 1 hour and then cooled. Next, transfer the polymerization solution to the separable flask No. 2 and add 90 g (5.0 mol) of water while stirring.
was added over 2 hours at room temperature. Thereafter, the temperature was raised to the boiling temperature of tetrahydrofuran, and the mixture was stirred for 2 hours while refluxing the tetrahydrofuran. Next, while boiling and refluxing the tetrahydrofuran, 500 g of ethyl acetate was added over 4 hours, and after stirring for a further 10 hours, stirring was stopped and the mixture was allowed to stand still for 20 hours while being naturally cooled. The polymerization solution was separated into a reddish-brown, low-viscosity upper layer and a pale yellow, high-viscosity lower layer, so both layers were separated and the tetrahydrophthalic acid content and butadiene-maleic acid copolymer content of each layer were determined by the method of Example 1. The results were analyzed and shown in Table 1. The reddish-brown coloring of the upper layer indicates that the polymerization catalyst residue was mainly distributed in the upper layer, and the absorption attributed to acid anhydride disappeared from the IR spectrum of the obtained copolymer, indicating that hydrolysis was not occurring. It was done perfectly. Example 5 294.3 g (3.0 mol) of maleic anhydride, 7.2 g of benzoyl peroxide and 2000 g of cyclohexanone were placed in a nitrogen-substituted autoclave No. 4 and heated to 80°C. Add isoprene to this solution.
204.6 g (3.0 mol) was continuously charged over 5 hours to carry out a copolymerization reaction. After the isoprene injection was completed, the reaction was continued for another hour. Next, 108 g (6 mol) of water was added over 2 hours while stirring at 80°C, and stirring was continued for 2 hours. Next, add 500g of cyclohexane while stirring at 80℃.
was added over a period of 3 hours, stirring was continued for 10 hours while maintaining the temperature at 80℃, and then cooled to 15℃.
Let it stand for a while. Separate the viscous lower layer from the resulting two-layer separated liquid, and add 95% by volume of acetone and 5% of water to this.
The lower layer was diluted by adding approximately the same volume of the mixed solvent consisting of % by volume as the removed upper layer. Next, this diluted solution was put into the autoclave again, heated to 80℃, and 500g of cyclohexane was added over 3 hours, and the temperature was lowered.
Stirring was continued for 5 hours while maintaining the temperature at 80°C, and then the mixture was cooled and left to stand. Since the autoclave internal liquid was separated into two layers, it was divided into a low viscosity upper layer and a high viscosity lower layer, and substituted tetrahydrophthalic acid (1-methylcyclohexene-4,5-dicarboxylic acid) and isoprene-maleic acid were separated in each layer. The copolymer content was analyzed and the values shown in Table 1 were obtained. Example 6 98.1 g (1.0 mol) of maleic anhydride, 1.6 g of azobisisobutyronitrile and 1000 g of acetone were placed in an autoclave purged with nitrogen and heated to 80°C. Then autoclave the isoprene 68.2
g (1.0 mol) was charged over 3 hours to carry out copolymerization. After the completion of isoprene charging, the reaction was continued for 1 hour and then cooled to stop the reaction. Transfer the polymerization solution in the autoclave to the separable flask in step 3,
While stirring at 50°C, 72 g (4.0 mol) of water was gradually added over 2 hours, followed by thorough stirring for another 5 hours. Next, while stirring the polymerization solution well, 300 g of toluene was added over 2 hours, and stirring was continued for 5 hours. The components contained in each layer were analyzed for both layers of the two-layer separated liquid obtained by allowing it to stand until the next day after the stirring was completed, and the values shown in Table 1 were obtained. Example 7 294.3 g (3.0 mol) of maleic anhydride, 4.9 g of azobisisobutyronitrile, and 1500 g of acetone were placed in a nitrogen-substituted autoclave No. 3.
heated to ℃. 162.3g of butadiene in this solution
(3.0 mol) was added over 6 hours. After the butadiene charging was completed, the reaction was continued for 1 hour at the same temperature and then cooled to stop the reaction. Next, this polymerization liquid was extracted, transferred to a separable flask No. 5, and heated to 50°C. Next water 324
g (18.0 mol) was added with stirring over 5 hours, followed by further stirring for 1 hour. After cooling to room temperature, 500 g of ethyl acetate was added over 5 hours while stirring thoroughly. After the addition was completed, stirring was continued for another 3 hours, and after the stirring was completed, the mixture was allowed to stand until the next day. The polymerization solution was separated into a reddish-brown, low-viscosity upper layer and a light-yellow, high-viscosity lower layer. were collected and analyzed using the method of Example 1, and the results are shown in Table 1.
obtained the value of Example 8 300 g of the hydrolyzed copolymer-rich lower layer separated in Example 7 was collected into a separable flask, and
The flask was equipped with a distillation device and a dropping funnel and heated in a water bath, and the solvent was distilled off and water was added dropwise at the same time to replace acetone and ethyl acetate in the lower layer with water. At this time, the water addition rate was made faster than the solvent distillation rate to control the copolymer concentration to gradually decrease. After the solvent was distilled off, a small amount of water was distilled off to completely drive out acetone and ethyl acetate. The final total amount of water added is 1050g
The aqueous solution at this time was a homogeneous solution when heated. The total weight of the final liquid is 1110g
The amount of copolymer in the lower layer initially collected is
Since the amount was 117 g (0.69 mol), the copolymer concentration of this aqueous solution was 10.5% by weight. Next, 100 g of an aqueous solution containing 27.4 g (0.69 mol) of sodium hydroxide was added to this aqueous solution in the heated state and stirred for 2 hours to obtain an aqueous solution of butadiene-maleic acid copolymer sodium salt. This aqueous solution remained homogeneous and transparent even after cooling, and could be consistently handled in a solution state during the synthesis of a copolymer sodium salt aqueous solution from a copolymerization reaction solution. Example 9 98.1 g (1.0 mol) of maleic anhydride, 1.6 g of azobisisobutyronitrile, and 750 g of dioxane were placed in a nitrogen-substituted autoclave No. 1 and heated to 70°C.
heated to. 88.6g of chloroprene in this solution
(1.0 mol) was charged over 2 hours to carry out copolymerization. After the completion of charging chloroprene, the reaction was continued for an additional hour and then cooled. Next, the polymerization solution was transferred to a separable flask (No. 2), heated to 70°C, and while stirring, 36 g (2.0 mol) of water was added over 3 hours, followed by stirring for 3 hours. Next, 150 g of n-heptane was added over 2 hours, stirred for another 2 hours, and left to stand until the next day. The content of substituted tetrahydrophthalic acid (1-chlorocyclohexene-4,5-dicarboxylic acid) and chloroprene-maleic acid copolymer in the resulting two-layer separated liquid was analyzed for each layer by the method of Example 1, and the table is shown. 1 result was obtained. 【table】

Claims (1)

[Claims] 1 When conjugated diene and maleic anhydride are solution copolymerized using a polymerization solvent and the conjugated diene-maleic anhydride copolymer is recovered from the copolymerization reaction solution, the anhydride used in the polymerization reaction is added to the copolymerization reaction solution. The copolymer and by-products are hydrolyzed by adding water in an amount equivalent to 10 times the amount of maleic acid, and then 0.05 to 2 parts by weight of water is added to 1 part by weight of the polymerization solvent in the copolymerization reaction solution. A recovery solvent that does not dissolve the decomposed copolymer and is compatible with the polymerization solvent is added and mixed to form a solution containing concentrated hydrolyzed copolymer and a solution containing hydrolyzed by-products. A method for recovering a conjugated diene-maleic anhydride copolymer, which comprises recovering the conjugated diene-maleic anhydride copolymer as a hydrolyzed purified copolymer by liquid-liquid separation.