JP2010024282A - Purification method of polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a purification method of a polymer, for efficiently and easily purifying a polymer by using only a small amount of a solvent. <P>SOLUTION: The purification method of a polymer aims to remove impurities in a polymer and comprises: generating a mixture solvent vapor from a solvent container 1 that houses a mixture solvent 2 of a good solvent for the polymer and a poor solvent for the polymer by heating the mixture solvent 2 and cooling and condensing the generated mixture solvent vapor to generate a liquefied mixture solvent; introducing the liquefied mixture solvent into a container 8 for a polymer solution that houses a polymer solution 9; permeating impurities through a filter 10 that is disposed on a side face or the bottom of the container 8 for the polymer solution and that permeates impurities included in the polymer solution 9 but does not permeate the polymer; and introducing the solvent containing the impurities permeated through the filter 10 into the above solvent container 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for purifying a polymer. More specifically, the present invention relates to a method for purifying a polymer, which can easily and efficiently purify a polymer using a polymer solution.

  When the monomer is polymerized, the resulting polymer has a low molecular weight such as an oligomer produced by the reaction of the monomers remaining in the raw material in addition to the target polymer. By-products are included as impurities.

  As a method for removing impurities contained in the polymer, a method of washing the polymer using a mixed solvent of a good solvent for the produced polymer and a poor solvent for the polymer has been proposed (for example, Patent Document 1). According to this method, the produced polymer dissolves in the good solvent but does not dissolve in the poor solvent. On the other hand, the impurities dissolve in the poor solvent, so that the polymer can be purified. However, in this method, in order to wash the produced polymer with a mixed solvent, a large amount of the mixed solvent is required, so that the load on the environment is large and the operation is complicated, and the single amount is not limited. There is a drawback that low-molecular-weight by-products generated when the body is polymerized tend to remain.

  As another method for removing impurities contained in the polymer, the polymer is dissolved in a good solvent for the polymer, and the resulting polymer solution is added to the poor solvent for the polymer. Then, a reprecipitation method in which the polymer is precipitated as a solid has been adopted (for example, see Patent Document 2). However, when the polymer is purified by this reprecipitation method, it takes a long time to purify the polymer, and not only complicated operation is required, but also a large amount of polymer cannot be purified at once. . Moreover, since solvent vapor | steam is discharge | released in air | atmosphere, the load to an environment is large, and there exists a possibility of an ignition depending on the kind of solvent.

JP-A-7-196725 JP-A-6-56998

  The present invention has been made in view of the prior art, and it is an object of the present invention to provide a polymer purification method capable of purifying a polymer efficiently and simply by using a small amount of solvent. And

  The present invention relates to a method for purifying a polymer that removes impurities contained in a polymer, wherein the mixing is performed from a solvent container containing a mixed solvent of a good solvent for the polymer and a poor solvent for the polymer. A mixed solvent vapor is generated by heating the solvent, and the generated mixed solvent vapor is cooled and condensed to produce a liquefied mixed solvent, and the produced liquefied mixed solvent is used for a polymer solution containing a polymer solution. Introduced into the container, the impurities contained in the polymer solution provided on the side surface or the bottom surface of the polymer solution container are allowed to permeate, but the impurities are permeated from a filter having pores that do not permeate the polymer, The present invention relates to a method for purifying a polymer, wherein a solvent containing impurities that have passed through a filter is introduced into the solvent container.

  According to the method for purifying a polymer of the present invention, there is an effect that the polymer can be purified efficiently and simply by using a small amount of solvent.

  The polymer purification method of the present invention is a polymer purification method for removing impurities contained in a polymer, and a solvent containing a mixed solvent of a good solvent for the polymer and a poor solvent for the polymer. The mixed solvent vapor is generated from the container by heating the mixed solvent, and the generated mixed solvent vapor is cooled and condensed to produce a liquefied mixed solvent, and the polymer solution is accommodated in the produced liquefied mixed solvent. The filter is introduced into the polymer solution container, and is provided on the side surface or bottom surface of the polymer solution container. The filter has a hole that transmits the impurities contained in the polymer solution but does not transmit the polymer. The method is characterized in that impurities are permeated and a solvent containing impurities permeated through a filter is introduced into the solvent container.

  The method for purifying the polymer of the present invention will be described with reference to FIG. FIG. 1 is a schematic explanatory view showing an embodiment of a purification apparatus that can be used in the method for purifying a polymer of the present invention, but the present invention is not limited to such an embodiment.

  The solvent container 1 contains a mixed solvent of a good solvent for the polymer and a poor solvent for the polymer.

  The good solvent for the polymer is a solvent having a solubility of 10% by weight or higher, preferably 15% by weight or higher, at normal temperature and normal pressure with respect to the polymer to be purified. It is desirable from the viewpoint of removing well. Since the good solvent for the polymer varies depending on the type of the polymer, it cannot be determined unconditionally. Therefore, it is preferable to appropriately determine the good solvent according to the type of polymer to be purified. As an example, when the polymer to be purified is an acrylic polymer, acetone or the like can be used as a good solvent for the acrylic polymer.

  Examples of impurities contained in the polymer include raw material monomers, low molecular weight by-products such as oligomers by-produced from the monomers, solvents used in the polymerization, and the like. .

  The poor solvent for the polymer is a solvent having a solubility of 3% by weight or less, preferably 2% by weight or less, at room temperature and normal pressure with respect to the polymer to be purified. This is desirable from the viewpoint of improving the yield without dissolving in a poor solvent. Since the poor solvent for the polymer varies depending on the type of the polymer, it cannot be determined unconditionally. Therefore, it is preferable to appropriately determine the poor solvent according to the type of polymer to be purified. As an example, when the polymer to be purified is an acrylic polymer, hexane or the like can be used as a poor solvent for the acrylic polymer.

  Note that both the good solvent and the poor solvent are preferably solvents having low reactivity with respect to the polymer from the viewpoint of preventing modification of the polymer to be purified.

  Examples of solvents used for good and poor solvents include aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, alcohol solvents, ketone solvents However, the present invention is not limited to such examples. Among these solvents, a good solvent and a poor solvent suitable for the polymer to be purified can be appropriately selected and used.

  The ratio between the good solvent and the poor solvent varies depending on the amount of impurities contained in the polymer and cannot be determined unconditionally. However, the ratio between the good solvent and the poor solvent (good solvent / poor solvent) : Volume ratio) is preferably 5/95 to 95/5, more preferably 10/90 to 90/10, and still more preferably 20/80 to 80/20.

  The amount of the mixed solvent 2 put in the solvent container 1 cannot be determined unconditionally because it varies depending on the amount of the polymer to be purified. Usually, the amount of the mixed solvent 2 is preferably about 300 to 1000 mL per 100 g of the polymer to be purified. In the so-called continuous washing method in which the polymer is washed with a conventional mixed solvent, the amount of the mixed solvent per 100 g of the polymer is 10 to 20 L (liter). Therefore, the purification method of the present invention is compared with the conventional method. There is an advantage that the amount of solvent can be remarkably reduced.

  A heating device 3 is attached to the solvent container 1. Examples of the heating device 3 include an oil bath and a heater. In the embodiment shown in FIG. 1, the mixed solvent 2 is indirectly heated from the outside of the solvent container 1. For example, by immersing a sheathed heater or the like in the mixed solvent 2, the mixed solvent 2 is directly You may heat. Although the heating temperature of the mixed solvent 2 varies depending on the type of the solvent used for the mixed solvent 2 and cannot be determined unconditionally, the mixed solvent 2 can usually be heated to about its azeotropic temperature. .

  The mixed solvent 2 may be stirred by putting a stirrer (not shown) such as a magnetic stirrer or a stirring blade into the mixed solvent 2 in the solvent container 1.

  The upper part of the solvent container 1 is connected to the polymer solution storage chamber 5 through a solvent vapor introducing pipe 4. The mixed solvent vapor generated by heating the mixed solvent 2 is introduced into the space in the polymer solution storage chamber 5 through the solvent vapor introduction pipe 4 and provided in the upper part of the polymer solution storage chamber 5. The cooling unit 6 rises. The mixed solvent vapor that has risen up to the cooling unit 6 is cooled by the cooling unit 7 by the cooling unit 7 and condensed to produce a liquefied mixed solvent. Examples of the cooling device 7 include a cooling device in which a pipe into which cooling water is introduced is wound.

  The produced liquefied mixed solvent travels along the inner wall of the cooling unit 6 and is dropped in the space in the polymer solution storage chamber 5 so as to be disposed in the lower part of the cooling unit 6 and stored in the polymer solution storage chamber 5. Into the polymer solution container 8. Therefore, by heating the mixed solvent 2, the mixed solvent 2 is supplied to the polymer solution 9 while changing into the mixed solvent vapor and the liquefied mixed solvent.

  A polymer solution 9 is accommodated in the polymer solution container 8. The polymer solution 9 may be a reaction mixture obtained by preparing a polymer, or may be one in which the solvent used for polymerization is removed from the reaction mixture in a certain amount in advance. However, from the viewpoint of reducing the amount of the solvent used in the polymerization as an impurity, it is preferable to remove the solvent as much as possible. The solvent contained in the reaction mixture is concentrated by, for example, a method of removing the solvent contained in the reaction mixture by reprecipitation of the polymer using a poor solvent, vacuum drying, heat drying, or the like. It can be removed by a method to do so.

  The solvent contained in the polymer solution 9 may be the solvent used when preparing the polymer, or may be replaced with the mixed solvent used in the present invention. The polymer solution 9 is concentrated, for example, by removing the solvent contained in the reaction mixture, and the polymer is recovered in a solid or high concentration, which is placed in the polymer solution container 8 and then liquefied. It may be prepared by dissolving or diluting a solid or high-concentration polymer by introducing a mixed solvent into the polymer solution container 8.

  The type of the polymer used in the polymer solution is not particularly limited as long as it dissolves or swells in a good solvent. Examples of polymers include (meth) acrylic acid polymers, (meth) acrylic acid ester polymers, acrylamide polymers, olefin polymers such as polyisobutylene, diene polymers such as polybutadiene, polystyrene, etc. Aromatic vinyl polymers, polyvinyl alcohol polymers, ethylene-vinyl acetate polymers, polyester polymers such as polyethylene terephthalate, polyamide polymers such as 6-nylon, polyurethane polymers, and the like. The present invention is not limited to such examples.

  Examples of the method for preparing the polymer include a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method, and the like, but the present invention is not limited to such examples. When a polymer is prepared by the bulk polymerization method, it is preferable to dissolve the obtained polymer in the mixed solvent in advance from the viewpoint of improving purification efficiency. When a polymer is prepared by a polymerization method such as a solution polymerization method, an emulsion polymerization method, or a suspension polymerization method, the resulting polymer contains a solvent, so that it can be used as it is as a polymer solution. In addition, the solvent may be removed in advance, or the solvent may be replaced with the mixed solvent.

  Although the content rate of the polymer in the polymer solution 9 is not particularly limited, it is usually preferably about 40 to 85% by weight, more preferably about 50 to 75% by weight from the viewpoint of increasing the purification efficiency of the polymer.

  There are no particular limitations on the shape, capacity, material, and the like of the polymer solution container 8 into which the polymer solution 9 is placed. Examples of the shape of the polymer solution container 8 include a cylindrical shape and a rectangular tube shape. Since the capacity of the polymer solution storage chamber 5 and the capacity of the polymer solution container 8 depend on the scale when the polymer is purified, it cannot be determined unconditionally. For example, when a large amount of polymer is purified at a time, the capacity of the polymer solution storage chamber 5 and the capacity of the polymer solution container 8 should be suitable for purifying a large amount of polymer. Preferably, the volume may not be as great when purification of the polymer at the laboratory level is required.

  The material of the polymer solution container 8 is not particularly limited as long as it is inactive with respect to the mixed solvent 2 and the polymer solution 9, but a representative example thereof is glass.

  The polymer solution container 8 is provided with a filter 10. As the filter 10, a filter having pores that transmits impurities contained in the polymer but does not transmit the polymer contained in the polymer solution 9 is used.

  Since the pore size of the filter 10 varies depending on the molecular weight of the polymer contained in the polymer solution 9 and the molecular weight of the impurity to be removed and cannot be determined unconditionally, the type of polymer, the molecular weight of the impurity, etc. It is preferable to select appropriately according to the conditions. A typical example of the filter 10 is a membrane filter made of a fluororesin. For example, by using a fluororesin membrane filter having a pore size of 1 μm or less, preferably 0.3 μm or less, a low molecular weight compound having a molecular weight of 1000 or less contained in the polymer can be efficiently removed. This has been confirmed by our study. A suitable filter 10 includes, for example, a membrane filter made of a resin such as a fluororesin having a pore diameter of 0.05 to 1 μm, preferably 0.05 to 0.3 μm.

  For example, as shown in FIG. 1, the filter 10 may be provided on the side surface of the polymer solution container 8, or may be provided on the bottom surface thereof. Since the liquefied mixed solvent is introduced from the upper part of the polymer solution container 8 by dropping along the inner wall of the cooling unit 6, from the viewpoint of increasing the removal efficiency of impurities contained in the polymer solution, the filter 10 Is preferably provided on the bottom surface opposite to the top of the polymer solution container 8.

  In addition, it is preferable from the viewpoint of increasing the purification efficiency that the polymer solution 9 in the polymer solution container 8 is, for example, a stirrer (not shown) such as a stirring blade and the polymer solution 9 is stirred.

  When the liquefied mixed solvent is introduced into the upper part of the polymer solution container 8, the liquid level of the polymer solution 9 in the polymer solution container 8 rises, but is present inside the polymer solution container 8. The residual monomer contained as an impurity contained in the polymer solution 9, a low molecular weight by-product such as an oligomer by-produced from the monomer, the solvent used during the polymerization, etc. are passed through the filter 10. It is discharged to the outside of the polymer solution container 8. At this time, the position of the liquid level of the polymer solution 9 present in the gap between the polymer solution storage chamber 5 and the polymer solution container 8 and the liquid level of the polymer solution 9 present in the polymer solution container 8 Are almost the same.

  The polymer solution storage chamber 5 and the solvent container 1 are connected to communicate with each other via a discharge pipe 11. Impurities that pass through the filter 10 and are discharged to the outside of the polymer solution container 8 are introduced into the solvent container 1 through the discharge pipe 11. In FIG. 1, the discharge pipe 11 extends upward to the bending point 11 a in order to make the liquid surface of the polymer solution 9 have a constant height in the polymer solution container 8. When the position of the bending point 11a is low, the amount of the polymer solution 9 is reduced and the purification efficiency is lowered. Therefore, the bending point 11a is preferably as high as possible, but the solution in the polymer solution storage chamber 5 is not preferred. Is preferably provided at a position lower than the lower part of the connecting portion 4a between the solvent vapor introducing tube 4 and the polymer solution storage chamber 5 so that the solvent vapor does not flow into the solvent vapor introducing tube 4.

  In the embodiment shown in FIG. 1, the position of the connecting portion 11 b between the polymer solution storage chamber 5 and the discharge pipe 11 is below the polymer solution storage chamber 5. This is preferable from the viewpoint of efficiently removing the solvent containing impurities discharged to the outside of the container 8. However, the connecting portion 11b does not necessarily have to be provided below the polymer solution storage chamber 5, for example, may be provided above the polymer solution storage chamber 5 (not shown), or may overlap. You may be provided in the intermediate part (not shown) of the united solution storage chamber 5 in the height direction.

  When the solvent containing impurities discharged to the outside of the polymer solution container 8 is introduced into the solvent container 1 via the discharge pipe 11, it mixes with the mixed solvent 2 in the solvent container 1, and the impurities are mixed into the mixed solvent 2. include. However, since the impurities contained in the mixed solvent 2 generally have a lower vapor pressure than the mixed solvent 2, they are converted into vapor when the mixed solvent 2 is heated and introduced into the polymer solution storage chamber 5 from the solvent vapor introducing pipe 4. It is hard to be done. Accordingly, the impurities discharged from the polymer solution container 8 stay in the solvent container 1 without being introduced into the polymer solution storage chamber 5, and therefore accumulate in the mixed solvent 2 in the solvent container 1. It becomes like this.

  Therefore, if the mixed solvent 2 is heated and the mixed solvent vapor is sent to the polymer solution storage chamber 5, a liquefied mixed solvent is generated, and the resulting liquefied mixed solvent is introduced into the polymer solution 9. As a result, the polymer solution 9 Are removed from the polymer solution 9 through the filter 10, and the removed impurities are accumulated in the mixed solvent 2.

  During the above operation, the polymer solution 9 in the polymer solution container 8 is sampled at an arbitrary time, and the purity of the polymer can be confirmed by, for example, gel permeation chromatography. it can.

  When the polymer has the desired purity, purification of the polymer can be completed. After completion of the purification of the polymer, the polymer solution container 8 is taken out from the polymer solution storage chamber 5, and then the purified polymer solution 9 is taken out from the polymer solution container 8, and this purified polymer is removed. By removing the solvent contained in the solution 9, the purified polymer can be recovered. The solvent contained in the polymer solution 9 can be easily removed by, for example, heat drying or vacuum drying.

  As shown in FIG. 1, since the operation can be performed in a closed system without contact with the outside air, the mixed solvent 2 can be prevented from leaking into the outside air, thereby preventing environmental pollution. Not only can this be done, but the risk of ignition can be avoided. In addition, since the mixed solvent 2 is circulated and used in the system, it is not necessary to use a large amount of solvent as in the case where the polymer is washed with a conventional solvent. There is an advantage that it can be reduced. Furthermore, since the polymer is purified only by heating the mixed solvent 2, there is an advantage that the polymer can be purified simply and efficiently without bothering manpower.

  Further, according to the purification method of the present invention, the time required for purification may be short, and the polymer is not discharged out of the system, so that a polymer having high purity can be obtained efficiently in high yield. .

  Next, the present invention will be described in more detail based on examples. However, the present invention is not limited to such examples.

Production Example 1
In a 5 L five-necked flask, 45 g of glycidyl methacrylate and 155 g of hydroxypropyl methacrylate as monomers, 6 g of 1-thioglycerol as a chain transfer agent, and 3800 g of propylene glycol monomethyl ether as a solvent were added, and the contents in the flask were added to a mechanical stirrer. While stirring, nitrogen gas was blown into the contents from a nitrogen gas inlet tube attached to the flask, and nitrogen gas replacement was performed for 1 hour.

  Next, after the temperature in the flask was raised to 75 ° C., 5 g of 2,2-azobis (2,4-dimethyl-4-methoxy) valeronitrile as a polymerization initiator was added to the content, and 80 ± Polymerization was carried out at a temperature of 2 ° C.

  When 4 hours have elapsed from the start of polymerization, 8 g of tertiary butyl peroxypivalate was added to the contents, and after 4 hours at a temperature of 80 ± 2 ° C., 4 g of tertiary butyl peroxypivalate was added, and another 8 hours. Cured. Thereafter, the flask is cooled to room temperature, the polymer solution in the flask is poured into a large amount of hexane, the polymer is precipitated, the supernatant solution is removed by decantation, the solid is dissolved in acetone, and then concentrated. The polymer A was recovered by drying it.

Production Example 2
In a 2 L five-necked flask, 21 g of benzyl acrylate and 64 g of hydroxypropyl acrylate as monomers and 1615 g of propylene glycol monomethyl ether as a solvent were added, and the contents in the flask were stirred with a mechanical stirrer and nitrogen attached to the flask. Nitrogen gas was blown into the contents from the gas inlet tube, and nitrogen gas replacement was performed for 1 hour.

  Next, after the temperature in the flask was raised to 75 ° C., 5 g of azobisisobutyronitrile as a polymerization initiator was added to the content, and polymerization was performed at a temperature of 80 ± 2 ° C.

  When 4 hours had elapsed from the start of polymerization, 0.4 g of azobisisobutyronitrile was added to the contents, followed by curing at a temperature of 80 ± 2 ° C. for 10 hours. Thereafter, the flask is cooled to room temperature, the polymer solution in the flask is poured into a large amount of hexane, the polymer is precipitated, the supernatant solution is removed by decantation, the solid is dissolved in acetone, and then concentrated. This was dried to recover the polymer B.

Examples 1-3
The purification apparatus shown in FIG. 1 was used. In a solvent container 1 having a capacity of 500 mL, 200 mL of a mixed solvent prepared by mixing a good solvent for the polymer (acetone) and a poor solvent for the polymer (n-hexane) at a ratio shown in Table 1 was added.

  In a 300 mL glass polymer solution container 8, 50 g of the polymer obtained in each of the production examples was separately placed, and the liquefied mixed solvent obtained by cooling the vapor of the mixed solvent was added to the liquefied mixed solvent. The polymer was dropped into the coalescence solution container 8 to dissolve the polymer to obtain a 20% polymer solution.

  A membrane filter (trade name: PORAFIL CM, pore size: 0.2 μm, manufactured by Central Scientific Trading Co., Ltd.) was provided as a filter 10 on the polymer solution container 8 on the bottom surface of the polymer solution container 8. A stirring blade (not shown) was placed in the polymer solution container 8 to stir the polymer solution 9.

  Purification was started by adjusting the temperature of the mixed solvent 2 to 50 ° C. using an oil bath as the heating device 3. The mixed solvent 2 in the solvent container 1 was stirred with a magnetic stirrer stirrer (not shown).

  During the purification, the polymer is sampled from the polymer solution 9 at an arbitrary time, and the purity of the polymer is confirmed by gel permeation chromatography and gas chromatography. The polymer solution container 8 is taken out from the polymer solution storage chamber 5, then the polymer solution 9 is taken out from the polymer solution container 8, and the solvent contained in the polymer solution 9 is removed to remove the polymer. The yield and molecular weight of the recovered and purified polymer were examined. The results are also shown in Table 1.

The yield and molecular weight of the polymer were examined according to the following method.
(1) Polymer Yield The polymer was deposited by reprecipitation method and dried and then quantified. Further, after the purified polymer is recovered and dried under reduced pressure for 1 day, its weight is measured, and the yield is determined based on the weight of this polymer and the weight of the polymer before purification.

(2) Molecular weight of polymer The number average molecular weight (Mn) and the weight average molecular weight (Mw) were examined by gel permeation chromatography (GPC) to determine the molecular weight distribution (Mw / Mn). The specific conditions are as follows.

Gel permeation chromatograph: manufactured by Tosoh Corporation, product number: HLC-8020
Column: manufactured by Tosoh Corporation, product number: TSKgel GMHXL, G4000HXL and G5000HXL are connected in series. Eluent: tetrahydrofuran, flow rate 1.0 mL / min
-Column temperature: 40 ° C
-Calibration curve: Created using standard polystyrene-Detection method: Differential refractive index (RI)

  In addition, the kind of polymer of Table 1 shows the kind of polymer obtained by each manufacture example. M represents the molecular weight of a single molecule determined from a calibration curve. Mw represents a weight average molecular weight, and Mn represents a number average molecular weight.

From the results shown in Table 1, the following can be understood.
From the results of Example 1, it can be seen that the amount of the polymer having a molecular weight of 1000 or more increases because the amount of the low molecular weight compound having a molecular weight of less than 1000 decreases as the purification time elapses.

  From the result of Example 2, when the volume ratio of hexane / toluene of the mixed solvent is 40/60, the molecular weight distribution (Mw / Mn) is 1.16 after 5 hours from the start of purification. It can be seen that an ideal polymer having a distribution (Mw / Mn) close to 1 is obtained, and a polymer having a molecular weight of 1000 or more accounts for 99.9% by weight, but the yield is low. On the other hand, from the result of Example 3, when the volume ratio of hexane / toluene of the mixed solvent is 60/40, the molecular weight distribution (Mw / Mn) is 1.27 after 12 hours from the start of purification. It can be seen that a polymer having a molecular weight distribution (Mw / Mn) larger than that of Example 2 is obtained, and a polymer having a molecular weight of 1000 or more occupies 99.8% by weight, resulting in a high yield.

  From these facts, according to the purification method of the present invention, the yield varies by adjusting the ratio of the good solvent and the poor solvent in the mixed solvent, but the molecular weight distribution (Mw / Mn) is close to 1. It can be seen that coalescence can be easily obtained.

  From the above, according to Examples 1 to 3, it can be seen that the content of impurities having a molecular weight of less than 1000 can be efficiently reduced to less than 1% by weight.

Comparative Example 1
It refine | purified by mixing 50 mL of 20% propylene glycol monomethyl ether solutions of the polymer A obtained in Production Example 1 and a mixed solvent of 300 mL of tetrahydrofuran and 150 mL of hexane, and reprecipitating the polymer A. As a result, the yield is 52.8% by weight, the content of the polymer A having a molecular weight of 1000 or more is as low as 98.1% by weight, and the amount of impurities having a molecular weight of less than 1000 exceeds 1% by weight. Thus, it was found that impurities having a molecular weight of less than 1000 were not sufficiently removed. When the molecular weight distribution (Mw / Mn) of the polymer A was examined, it was 6200/4700 (1.31).

Comparative Example 2
The 20% propylene glycol monomethyl ether solution of Polymer B obtained in Production Example 2 was mixed with a mixed solvent of 200 mL of tetrahydrofuran and 200 mL of hexane to purify the polymer B by reprecipitation. As a result, the yield is 20% by weight, the content of the polymer B having a molecular weight of 1000 or more is as low as 98.2% by weight, and the amount of impurities having a molecular weight of less than 1000 exceeds 1% by weight. It was found that impurities having a molecular weight of less than 1000 were not sufficiently removed. When the molecular weight distribution (Mw / Mn) of the polymer B was examined, it was 6500/4400 (1.48).

  From the above results, according to the purification method of each example, it is possible to easily remove low molecular weight impurities selectively only by using a small amount of solvent as compared with the conventional method of each comparative example. As a result, it can be seen that a polymer having a high molecular weight of 1000 or more and a low number average molecular weight can be recovered in a high yield.

Experimental example 1
In Example 1, the number average molecular weight (Mn) of the impurities contained in the mixed solvent in the solvent container 1 after purifying the polymer A before purification, the polymer A after purification, and the polymer A is as above. The gel permeation chromatography (GPC) was similarly examined. The result is shown in FIG.

  In FIG. 2, symbol A is a chart showing the GPC measurement results of impurities contained in the mixed solvent in the solvent container 1 after the polymer A is purified, and symbol B is the polymer A after the polymer A is purified. The chart which shows the measurement result of GPC of this, and the code | symbol C show the chart which shows the measurement result of GPC of the polymer A before refine | purifying the polymer A. FIG.

  From the results shown in FIG. 2, a chart (symbol B: purified product) showing the measurement results of GPC of polymer A after purification of polymer A, and GPC of polymer A before purification of polymer A In the chart showing the GPC measurement result of the polymer A after purification, the low molecular weight polymer before purification on the right side of the peak of the chart Since the portion to be shown is cut, it can be seen that the low molecular weight compound is selectively removed by purification. This is supported by the fact that a chart indicating the presence of a low molecular weight compound is detected in the chart (symbol A: mother liquor) showing the GPC measurement result of the mixed solvent in the solvent container 1 after the polymer A is purified. It is done.

It is a schematic explanatory drawing which shows one embodiment of the refiner | purifier used for the purification method of the polymer of this invention. In Experimental example 1 of this invention, it is a graph which shows the measurement result of the gel permeation chromatography of the polymer A before and after refinement | purification, and the mixed solvent after refinement | purification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Solvent container 2 Mixed solvent 3 Heating apparatus 4 Solvent vapor | steam inlet tube 4a Connection part of a solvent vapor inlet tube and a polymer solution storage chamber 5 Polymer solution storage chamber 6 Cooling part 7 Cooling device 8 Polymer solution container 9 Polymer Solution 10 Filter 11 Discharge pipe 11a Bending point 11b Connection portion between polymer solution storage chamber and discharge pipe

Claims (1)

  A method for purifying a polymer that removes impurities contained in the polymer, wherein the mixed solvent is heated from a solvent container containing a mixed solvent of a good solvent for the polymer and a poor solvent for the polymer. The mixed solvent vapor is generated, and the generated mixed solvent vapor is cooled and condensed to generate a liquefied mixed solvent, and the generated liquefied mixed solvent is introduced into a polymer solution container containing the polymer solution. Then, the impurities contained in the polymer solution, which are provided on the side surface or the bottom surface of the polymer solution container, permeate through the filter having pores that do not permeate the polymer, and permeate the filter. A method for purifying a polymer, comprising introducing a solvent containing impurities into the solvent container.