JPS6160087B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for purifying and recovering a copolymer of a conjugated diene and maleic anhydride, in which a purified copolymer concentrate is recovered in high yield and with good purity from a copolymerization reaction product of a conjugated diene and maleic anhydride. It is about the method. 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. By the way, in the copolymerization reaction of a conjugated diene and maleic anhydride, a part of the conjugated diene and maleic anhydride cause a Diels-Alder reaction, resulting in the formation of tetrahydrophthalic anhydride or substituted tetrahydrophthalic anhydride (in the present invention, the following It is well known that these products (abbreviated as THPA) are produced as by-products. In addition, in the copolymerization reaction of conjugated diene and maleic anhydride, it is necessary to use a good solvent for the copolymer (for example, a polar solvent such as cyclohexanone, acetone, dioxane, tetrahydrofuran, dimethyl sulfoxide, etc.) as a polymerization solvent. It is well known that if polymerization is not performed, the resulting copolymer will undergo gelation during the copolymerization reaction and lose its commercial value. Furthermore, when a copolymerization reaction solution containing a copolymer of conjugated diene and maleic anhydride is brought into contact with water, both by-products and maleic anhydride units in the copolymer undergo hydrolysis and dissolve in hot water, or It becomes a rubbery paste-like substance that is difficult to handle. Due to the specificity of the copolymerization reaction of conjugated diene and maleic anhydride and the specificity of the copolymer, there are conventional methods for recovering the polymer from the polymerization reaction mixture (e.g., by blowing steam into the polymerization solution and steaming the solvent). (recovering the polymer by stripping, etc.)
It is difficult to purify and recover the copolymer. Therefore, a method for recovering a conjugated diene-maleic anhydride copolymer from a polymerization reaction solution in high yield and purity (that is, sufficiently removing THPA without impairing commercial value) has been desired. Conventionally, the method for recovering conjugated diene-maleic anhydride copolymer from a copolymerization reaction mixture (copolymerization reaction solution) is to use a good solvent for THPA and a poor solvent for the copolymer (substantially The copolymerization reaction mixture is precipitated by using a large amount of a solvent that does not dissolve the copolymer, such as aromatic hydrocarbons such as benzene, toluene, and xylene, or halogenated hydrocarbons such as methylene chloride and chloroform, as a precipitant. A method is adopted in which THPA is gradually added to precipitate the copolymer into a powder or lump, and at the same time, THPA is dissolved in the precipitant. This copolymer recovery method has the advantage of reliably removing THPA, but on the other hand, it is necessary to use an extremely large amount of precipitation solvent to separate and recover a small amount of copolymer, and this method is not suitable for industrial use. The major disadvantage of carrying out 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 method of recovering purified copolymer from a copolymerization reaction mixture, 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 (Japanese Patent Publication No. 46-29725). 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,
We have arrived at the present invention. According to the method of the present invention, not only the recovery rate of the copolymer from the copolymerization reaction product is very high, but also the removal rate of by-product THPA is very high, and the removal of polymerization catalyst residue is easy, resulting in commercial value. A copolymer with a high carbon content can be recovered by an industrially easily practicable means. The method of the present invention involves solution copolymerizing a conjugated diene and maleic anhydride using a polymerization solvent, and purifying and recovering the conjugated diene-maleic anhydride copolymer from the copolymerization reaction solution.
(per 1 part of polymerization solvent in the copolymerization reaction solution) of a recovery solvent that does not dissolve the copolymer but is compatible with the polymerization solvent and mix, concentrate the copolymer, and remove the containing solution and by-products. The present invention relates to a method for purifying and recovering a conjugated diene-maleic anhydride copolymer, which comprises separating the copolymer into a solution containing the copolymer, concentrating the copolymer, and recovering the solution containing the copolymer. In the present invention, parts represent parts by weight. 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 these polymerization solvents include cyclohexanone, acetone, dioxane, tetrahydrofuran, dimethyl sulfoxide, and methyl ethyl ketone. 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, radical initiators and ionizing radiation are typically used. Further, the polymerization temperature is not particularly limited, but is generally carried out at 30 to 100°C. By such polymerization, a copolymerization reaction solution (polymerization reaction mixture) having a copolymer concentration of usually 7 to 40% by weight, preferably 10 to 25% by weight is obtained. This copolymerization reaction solvent also contains by-products such as THPA. The present invention relates to purifying and recovering a copolymer from this polymerization reaction solution, and a predetermined recovery solvent is added to this polymerization reaction solution. The copolymer recovery solvent used in the present invention refers to the conjugated diene-maleic anhydride copolymer that is usually used at room temperature.
A solvent that cannot be substantially dissolved in a temperature range of 100°C, and a solvent that is compatible with the polymerization solvent, such as n-butane, i-butane,
n-pentane, iso-pentane, n-hexane,
iso-hexane, n-heptane, iso-heptane,
Aliphatic hydrocarbons such as n-octane, or alicyclic hydrocarbons such as cyclopentane and cyclohexane, aromatic hydrocarbons such as benzene, toluene, and xylene, and halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and chlorobenzene. or halogenated aromatic hydrocarbons, ethyl acetate,
These include aliphatic or aromatic ester compounds such as butyl acetate and ethyl benzoate. Of course, these recovered solvents can also be used as a mixture of two or more. The amount of recovered solvent to be added to the copolymerization reaction solution in the present invention naturally depends on the composition of the copolymerization reaction product, but in general, it is 0.05 to 1 part of the polymerization solvent in the copolymerization reaction solution. Part to 2 parts, preferably 0.1 part to 1.0 part. If the amount of recovery solvent used is small, the recovery rate of the copolymer will be low, and if too much recovery solvent is added, the recovery rate of the copolymer will be high, but the viscosity of the solution layer containing a large amount of copolymer will increase. This makes handling 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, the recovered solvent may be added little by little to the copolymerization reaction solution while thoroughly stirring it over a period of 10 minutes to 5 hours, or in some cases, the recovered solvent may be added while stirring the copolymerization reaction solution well. Almost instantaneous addition is also possible. There is no particular restriction on the temperature of the copolymerization reaction solution when adding the recovered solvent, and it is possible to carry out the reaction in a temperature range of 0°C to 100°C, for example. After adding the recovered solvent to the copolymerization reaction solution,
This mixture is usually heated at 0°C to 200°C, preferably at 10°C.
Stirring is performed at a temperature range from ℃ to 150℃ for 10 minutes to 40 hours, preferably 30 minutes to 20 hours, to form a solution layer (or droplets) rich in copolymer and a solution layer (or droplets) rich in by-product THPA. It is desirable to reach a distributional equilibrium of . 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 separation of liquids, a solution containing a copolymer more concentrated than the copolymer concentration in the initial copolymerization reaction solution is obtained on one side, and a solution rich in by-product THPA is obtained on the other. It is characterized by the fact that a solution can be obtained. Generally, a solution rich in copolymers will be in the lower layer, and a solution containing by-product THPA will be in 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 copolymers will be in 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 vessel 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. It is. 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. Separation of the copolymer from a solution rich in the copolymer recovered and purified from the copolymerization reaction solution by the method of the present invention can also be carried out by, for example, removing the solvent by directly drying this solution. It is also possible to precipitate and recover the copolymer by adding it to a poor solvent that does not dissolve the copolymer. When the copolymer is recovered by the latter method, there is an advantage that the amount of poor solvent used can be extremely small because the copolymer concentration is high. Furthermore, water may be added to a solution enriched with the purified and recovered copolymer, the solvent may be distilled off, and the copolymer may be recovered as an aqueous solution or an aqueous suspension of the hydrolyzed copolymer. 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, the solution enriched in the copolymer separated and recovered in the first stage copolymer recovery operation is Then, a solvent for dissolving the copolymer (same type as the polymerization solvent) is added to obtain a solution with a composition ratio close to that of the copolymer and polymerization solvent in the initial copolymerization solution, and then the method of the present invention is applied. Therefore, it can be carried out by adding a recovery solvent. As mentioned above, according to the method of the present invention, the recovery rate of the copolymer from the copolymerization reaction product is high, and by-products are reduced.
It has the advantage that a copolymer with high commercial value, which has a high removal rate of TAPA and also a high removal rate of catalyst residue, can be produced by an extremely simple operation and economically. The features of the present invention will be explained in more detail with reference to Examples below. Example 1 29.4 g (0.3 mol) of maleic anhydride and 180 g of cyclohexanone were placed in a nitrogen-substituted autoclave.
g and 0.5 g of benzoyl peroxide were added and heated to 70°C. 16.2 g of butadiene for this solution
(0.3 mol) was continuously charged over a period of 1 hour.
After the charging of butadiene was completed, the copolymerization reaction solution was further reacted at 70°C for 1 hour. Next, while maintaining this copolymerization reaction mixture at 70 DEG C., 72 g of n-hexane (ie, 0.4 parts per part of cyclohexanone as a polymerization solvent) was added over 1.5 hours, and the mixture was stirred for an additional 2 hours. The mixture was then allowed to stand for 15 hours and separated into a brown upper layer rich in tetrahydrophthalic anhydride and a slightly yellow lower layer rich in butadiene-maleic anhydride copolymer. The contents of tetrahydrophthalic anhydride and butadiene-maleic anhydride copolymer in the upper and lower layers were respectively determined by gas chromatography and a polymer precipitation fractionation method using benzene as a precipitant, and the following results were obtained.

[Table] Example 2 294.2 g of maleic anhydride, 1600 g of acetone, and 1.6 g of azobisisobutyronitrile were added to the autoclave No. 3 purged with nitrogen, and the internal temperature was
It was heated to 70°C. Then butadiene
162.3 g was charged into the autoclave at a constant rate over 5 hours, and polymerization was continued for an additional hour after the butadiene was filled. This polymerization reaction mixture was transferred to a separable flask (No. 5), and 610 g of benzene was added thereto over 1 hour while stirring well. The mixture was then kept stirring at 70° C. for 3 hours and then allowed to stand at room temperature for 20 hours. It was found that the reddish brown solution in the upper layer was rich in tetrahydrophthalic anhydride, and the slightly yellow solution in the lower layer had a high copolymer content. When each layer was analyzed according to Example 1, the following results were obtained.

[Table] Since the lower layer containing the copolymer is only slightly colored, it is clear that the catalyst residue is separated into the upper layer. Example 3 39.8 g of monochloromaleic anhydride and 300 g of tetrahydrofuran were placed in an autoclave purged with nitrogen.
g and 1 g of benzoyl peroxide were added and heated to 75°C. 20.4 g of isoprene was continuously added to this solution over a period of 2 hours. After charging of isoprene was completed, this copolymerization reaction mixture was further reacted at 75°C for 1 hour. Next, while maintaining this copolymerization reaction mixture at 75° C., 150 g of n-heptane was added within 30 minutes, and stirring was continued for an additional hour. The mixture was then cooled to room temperature and allowed to stand for 15 hours. The amounts of substituted tetrahydrophthalic anhydride and copolymer were determined for the upper and lower layers by gas chromatography and polymer precipitation using benzene as a precipitant, respectively, and the following results were obtained.

[Table] The intrinsic viscosity at 30° C. of a tetrahydrofuran solution of the copolymer obtained by drying the lower copolymer solution under reduced pressure was 0.63. Examples 4 to 7 After the autoclave of 4 was purged with nitrogen, 294.2 g of maleic anhydride, 3.5 g of azobisisobutyronitrile and 1920 g of acetone were added and heated to 65°C. Next, 162.3 g of butadiene was continuously poured into this solution over a period of 3 hours while controlling the temperature from 65°C to 70°C. After charging the butadiene, the copolymerization reaction mixture was further heated to 65° C. for 1 hour. Next, the copolymerization reaction mixture was cooled to room temperature, and 500 g was placed in one flask that was purged with nitrogen.
Then, n-hexane was added to this at various ratios over the course of 1 hour, followed by stirring for 3 hours, and the mixture was allowed to stand at room temperature for 15 hours, separated into an upper layer and a lower layer, and each layer was processed. Analyzed according to the method of Example 1. The results obtained are shown in Table 1.

[Table] Example 8 300 g of acetone was added to 150 g of the lower layer with high copolymer content separated and recovered in Example 6 and stirred thoroughly to form a homogeneous solution. Next, 160 g of n-hexane was added to this solution over 1 hour while stirring, and stirring was continued for 3 hours after the addition was completed. This mixture was allowed to stand at room temperature for 15 hours, and the separated upper and lower layers were analyzed, and the following results were 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 purified and recovered from the copolymerization reaction solution, 0.05 to 2.0 parts by weight are added to the copolymerization reaction solution. A recovery solvent that does not dissolve the copolymer (per 1 part by weight of polymerization solvent in the copolymerization reaction solution) and is compatible with the polymerization solvent is added and mixed, and the copolymer is concentrated and the containing solution and by-products are separated. 1. A method for purifying and recovering a conjugated diene-maleic anhydride copolymer, which comprises separating the copolymer into a solution containing the copolymer, concentrating the copolymer, and recovering the solution containing the copolymer.