JP2013237806A - Purification method of polymer solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification method of a polymer solution, by which from a polymer solution that contains at least lithium and/or titanium, these metallic residues are efficiently removed to obtain a purified polymer solution.SOLUTION: A purification method of a polymer solution includes: a process 1 that prepares a polymer solution that contains an organic solvent whose solubility parameter is less than 20 (MPa)and that contains at least lithium and/or titanium; a process 2 in which the polymer solution is added with a nonaqueous liquid whose solubility parameter is 20-40 (MPa)by 0.0001-0.01 volume times and is mixed under a condition of ((P/V)T value)≥100 to obtain a mixture liquid; and a process 3 in which the mixture liquid is added with water of 0.1-10 volume times and is mixed under a condition of a (P/V)T value≥100.

Description

  The present invention relates to a method for purifying a polymer solution.

  In recent years, thermoplastic elastomers, which are soft materials having rubber elasticity, do not require a vulcanization process, and can be molded and recycled in the same manner as thermoplastic resins, are widely used in a wide range of fields.

  For example, a polymer of a conjugated diene monomer such as 1,3-butadiene or isoprene, or a vinyl aromatic monomer such as styrene copolymerizable with the conjugated diene monomer and the conjugated diene monomer. The copolymer with the body is very important as a modifier for impact-resistant transparent resin, polyolefin, or polystyrene resin.

  In addition, hydrogenated polymers obtained by adding hydrogen to the olefinic double bond portion contained in the conjugated diene polymer take advantage of the excellent weather resistance, and are used for automobile parts, home appliance parts, electric wire coatings, medical parts. , Used for sundries, footwear, etc.

  Generally, the conjugated diene polymer is produced by living anionic polymerization using an alkyl lithium as an initiator. Further, after the polymerization, a hydrogenation reaction (hereinafter, also referred to as “hydrogenation reaction”) is performed on the olefinic double bond portion using a Group VIII or Group IV metal as a catalyst in the periodic table, whereby the hydrogenated polymer is obtained. Can be obtained.

  Various methods for hydrogenating a polymer having an olefinic double bond have been reported. For example, suitable compounds such as compounds of Group VIII of the periodic table, particularly nickel or cobalt compounds and alkylaluminum compounds can be used. A hydrogenation method using a catalyst combined with a reducing agent is known. In addition, a titanium compound which is a group IV metal of the periodic table, for example, a bis (cyclopentadienyl) titanium compound and a catalyst in which an appropriate reducing agent such as an alkylaluminum compound is combined is used. Methods for hydrogenating unsaturated double bonds of polymers are known.

  As described above, thermoplastic elastomers, particularly conjugated diene polymers such as those described above, and hydrogenated polymers thereof include metal residues (hereinafter referred to as “catalyst residues”) derived from initiators and hydrogenation catalysts. Will be included). The metal residue in the polymer solution must be removed efficiently in the manufacturing process because it leads to various quality degradations such as product roughness, surface roughness, coloring, and turbidity.

  In order to solve this problem, several proposals have been made as a method for removing the metal residue remaining in the polymer solution.

  For example, Patent Document 1 discloses a method of removing a lithium residue in a polymer solution by vigorously mixing the polymer solution and water using a rotary disperser having a meshing structure.

  Patent Document 2 discloses a method of removing residues of Group VIII metals in the periodic table including nickel using an oxidizing agent and dicarboxylic acid. Further, Patent Document 3 discloses a method for removing residues of Group VIII metals in the periodic table including nickel by a method of adsorbing to silicate. In addition to the above, removal of lithium and group VIII metals of the periodic table has been disclosed in a number of prior literatures.

  On the other hand, there has been almost no report on a method for removing a titanium residue. For example, Patent Document 4 discloses removal of a titanium residue using an inorganic acid, an alcohol, and water. The removal of titanium residues using organic acids, alcohols and water is only disclosed.

Japanese Patent Laid-Open No. 6-136034 US Pat. No. 4,595,749 US Pat. No. 5,104,972 JP 2002-167406 A JP 2009-91574 A

  Metal residues that cause product quality deterioration need to be efficiently removed from the polymer solution. However, as described above, in the prior art, there have been few reports on removal methods that have a high effect on lithium and titanium among a plurality of metal residues. Further, in the methods described in Patent Documents 4 and 5, it is necessary to use a large amount of alcohol and water at the time of metal removal, and waste liquid treatment becomes a big problem in industrial production.

  The present invention has been made in view of the above problems, and is a polymer solution that efficiently removes these metal residues from a polymer solution containing at least lithium and / or titanium to obtain a purified polymer solution. A purification method is provided.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have a specific solubility parameter (hereinafter abbreviated as SP value) for a polymer solution containing at least lithium and / or titanium. By mixing water under specific conditions with respect to the liquid mixture obtained by mixing the aqueous liquid under specific conditions, good compatibility between the polymer solution phase and the aqueous phase is expressed and mixed. The inventors have found that the subsequent separation state is also good, and found that a high metal removal effect can be obtained thereby completing the present invention.
That is, the present invention is as follows.

[1]
Step 1 for preparing a polymer solution containing an organic solvent having a solubility parameter of less than 20 (MPa) ^1/2 and containing at least lithium and / or titanium;
A non-aqueous liquid having a solubility parameter of 20 to 40 (MPa) ^1/2 is added by 0.0001 to 0.01 volume times with respect to the polymer solution, and the condition (P / V) · T value ≧ 100 is satisfied. Step 2 of obtaining a mixed solution by mixing;
Step 3 of adding 0.1 to 10 times volume of water to the mixture, and mixing under the condition of (P / V) · T value ≧ 100;
A method for purifying a polymer solution comprising:
[2]
The method for purifying a polymer solution according to the above [1], wherein the solubility parameter of the organic solvent is in the range of 14-18.
[3]
The method for purifying a polymer solution according to [1] or [2], wherein the solubility parameter of the non-aqueous liquid is in the range of 23 to 37.
[4]
The method for purifying a polymer solution according to any one of [1] to [3], wherein the non-aqueous liquid is alcohol.
[5]
The method for purifying a polymer solution according to any one of [1] to [4], wherein the polymer solution further contains aluminum.

  According to the present invention, the lithium and / or titanium residue remaining in the polymer solution is mixed with the polymer solution, a non-aqueous liquid having a specific SP value, and water under specific conditions, thereby improving efficiency. And a polymer solution with little metal residue can be obtained.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist.

[Polymer solution purification method]
The method for purifying the polymer solution of the present embodiment includes a step 1 of preparing a polymer solution containing an organic solvent having a solubility parameter of less than 20 (MPa) ^1/2 and containing at least lithium and / or titanium;
A non-aqueous liquid having a solubility parameter of 20 to 40 (MPa) ^1/2 is added by 0.0001 to 0.01 volume times with respect to the polymer solution, and the condition (P / V) · T value ≧ 100 is satisfied. Step 2 of obtaining a mixed solution by mixing;
Step 3 of adding 0.1 to 10 times volume of water to the mixed solution and mixing under the condition of (P / V) · T value ≧ 100.

[Step 1]
In the method for purifying a polymer solution according to the present embodiment, the step 1 includes a step of comprising an organic solvent having a solubility parameter of less than 20 (MPa) ^1/2 (ie, an SP value of less than 20) and containing at least lithium and / or titanium. This is a step of preparing a coalescence solution.

The SP value is, for example, R.R. T. T. et al. It can be determined by the method described in Fedors, Polymer Engineering and Science, (14), 147 (1974).
The term “SP value” described in the present specification is a numerical value when (MPa) ^1/2 is used as a unit. Conversion of the unit of the solubility parameter can be performed by the following formula.
1 (cal / cm ³ ) ^1/2 ≒ 2.05 (J / cm ³ ) ^1/2 ≒ 2.05 (MPa) ^1/2

(Polymer solution containing at least lithium and / or titanium)
The polymer solution purified in the present embodiment contains at least lithium, titanium, or both, and may further contain aluminum. An example of such a polymer solution is a hydrogenated conjugated diene copolymer solution. In this embodiment, a conjugated diene polymer solution before the hydrogenation reaction can be prepared as the polymer solution to be purified.

  The hydrogenated conjugated diene copolymer solution is produced, for example, by subjecting a conjugated diene polymer polymerized by a lithium polymerization catalyst to a hydrogenation reaction under a catalyst containing a titanium compound and various reducing agents. be able to.

(Polymer)
The conjugated diene polymer is not particularly limited as long as it is generally used in the art, but specifically, a conjugated diene homopolymer or a conjugated diene monomer having a number average molecular weight of 500 to 1,000,000. Random, tapered or block copolymers of the polymer and vinyl aromatic monomers can be used, and hydrogenation is possible for the unsaturated double bond of these conjugated diene units.

  The number average molecular weight can be measured in terms of polystyrene using gel permeation chromatography (GPC).

  The conjugated diene monomer that can be used is not particularly limited, and specifically, 1,3-butadiene, isoprene, piperylene, phenylbutadiene, 3,4-dimethyl-1,3-hexadiene, 4,5-diethyl. Examples include conjugated diene compounds containing 4 to 12 carbon atoms such as -1,3-octadiene. Among these, it is preferable to use 1,3-butadiene and isoprene. The vinyl aromatic monomer copolymerizable with the conjugated diene monomer is not particularly limited. Specifically, styrene, α-methylstyrene, styrene substituted with an alkoxy group, 2-vinyl Vinyl allyl compounds such as pyridine, 4-vinyl pyridine, vinyl naphthalene and vinyl naphthalene substituted with alkyl groups can be used. Among these, it is preferable to use styrene and α-methylstyrene.

  When a conjugated diene monomer and a vinyl aromatic monomer are mixed to produce a copolymer, for example, a conjugated diene monomer: vinyl aromatic monomer (weight ratio) = 5: 95. It is preferable to set it to -95: 5. By setting such a weight ratio, a copolymer having excellent impact resistance and good product processability can be obtained.

  Such a conjugated diene polymer is produced by a polymerization method generally used in this field. In this embodiment, for example, a conjugated diene polymer can be obtained by anionic polymerization using an organolithium compound as an initiator. Specific examples of the organic lithium compound include n-butyllithium and s-butyllithium. The amount of such an initiator used is generally used in this field, and can be freely adjusted according to the molecular weight of the target polymer. Thereafter, a hydrogenated conjugated diene polymer can be produced by performing a hydrogenation reaction on the obtained polymer solution.

(Hydrogenation reaction)
In the hydrogenation reaction, the polymer solution is maintained at a constant temperature in an inert gas atmosphere such as hydrogen, helium, argon, or nitrogen, and then a hydrogenation catalyst is added in a stirred or unstirred state, and hydrogen gas is supplied at a constant pressure. It is preferable to carry out by injecting. Furthermore, the temperature of the hydrogenation reaction is preferably 30 to 150 ° C., and the pressure is preferably ^{2 to} 30 kg / cm ² .

  When the temperature of the hydrogenation reaction is within the above range, the reactivity is improved and a sufficient reaction yield can be obtained, and a side reaction due to thermal degradation of the polymer can be suppressed. When the pressure of the hydrogenation reaction is within the above range, the reaction rate is improved, the reaction time is shortened, and the cost of investing in the reactor can be suppressed, which is economically preferable.

  The hydrogenation catalyst is a conjugated diene polymer having a number average molecular weight of 500 to 1,000,000, or a random, tapered, block copolymer of a conjugated diene and a vinyl aromatic monomer, and is used for unsaturated double bonds of conjugated diene units. On the other hand, it can be selectively hydrogenated.

  The polymer concentration in the polymer solution in Step 1 is not particularly limited, but is preferably 5 to 50% by mass, and more preferably 10 to 25% by mass. When the polymer concentration is within the above range, productivity is improved, and an increase in viscosity is suppressed and metal removal efficiency is improved.

  The titanium compound used in the hydrogenation reaction is not particularly limited as long as it is generally used in the art, and examples thereof include a cyclopentadienyl titanium compound, such as cyclopentadienyl titanium halide, Cyclopentadienyl (alkoxy) titanium dihalide, bis (cyclopentadienyl) titanium dihalide, bis (cyclopentadienyl) titanium dialkylate, bis (cyclopentadienyl) titanium diallylide and bis (cyclopentadienyl) ) It is selected from titanium dialkoxy compounds. These can be used alone or in combination.

  The titanium compound is preferably used in an amount of 0.01 to 20 mmol per 100 g of conjugated diene polymer, more preferably 0.05 to 5 mmol per 100 g of polymer. When the amount of the titanium compound used is within the above range, the hydrogenation reaction rate is improved, the productivity is improved, and the amount of unnecessary catalyst is small, which is economically preferable. The amount of chemical substances used can be reduced.

  The reducing agent used together with the titanium compound is not particularly limited as long as it is a reducing agent generally used in the art, and examples thereof include alkylaluminum compounds, alkylmagnesium compounds, organolithium compounds, and metal hydrides. These can be used alone or in combination. This embodiment is also effective in removing lithium and aluminum residues contained in the polymer solution. Therefore, among the above reducing agents, it is preferable to use an alkylaluminum compound or an organolithium compound from the viewpoint of obtaining a polymer solution with a small amount of metal residue.

  The hydrogenation reaction using the titanium-based catalyst is not particularly limited, and specifically, WO 00/08069, US Pat. No. 4,501,857, US Pat. No. 4,673, No. 714, US Pat. No. 4,980,421, US Pat. No. 5,753,778, US Pat. No. 5,910,566, US Pat. No. 6,020,439 It can be carried out using the method described in the specification and the like.

(Organic solvent)
In the present embodiment, the solvent of the polymer solution prepared in step 1 is an organic solvent having a solubility parameter of 20 (MPa) less than ^1/2 (SP value of less than 20). Although it does not specifically limit as an organic solvent with SP value less than 20, Specifically, n-pentane (SP value = 14.4), n-hexane (SP value = 14.9), n-heptane (SP value) = 15.3), n-octane (SP value = 15.5), cyclohexane (SP value = 16.8), diethyl ether (SP value = 15.4), tetrahydrofuran (SP value = 18.6), ethylbenzene (SP value = 18.0), xylene (SP value = 18.0), toluene (SP value = 18.2) and the like. In the present embodiment, these organic solvents having an SP value of less than 20 can be used alone or in combination.

  The solubility parameter (SP value) of the organic solvent is preferably 12 to 19, more preferably 13 to 18.5, and even more preferably 14 to 18. By making SP value into the said range, the non-aqueous liquid mentioned later acts as an effective compatibilizer with respect to a polymer solution phase and an aqueous phase, and, as a result, the outstanding metal removal effect is acquired, and it is preferable.

[Step 2]
In the method for purifying a polymer solution of the present embodiment, in Step 2, a non-aqueous liquid having a solubility parameter of 20 to 40 (MPa) ^1/2 (ie, SP value of 20 to 40) was obtained in Step 1. In this step, 0.0001 to 0.01 times the volume of the polymer solution is added and mixed under the condition that the (P / V) · T value is 100 or more.

  In step 2, the polymer solution obtained in step 1, for example, lithium or titanium residue contained in the hydrogenated conjugated diene polymer solution is sufficiently brought into contact with the non-aqueous liquid, thereby allowing step 3 to occur. The purpose of this is to facilitate the transfer of lithium and titanium residues to the aqueous phase.

(Non-aqueous liquid)
The solubility parameter of the non-aqueous liquid is in the range of 20 to 40 (MPa) ^1/2 (SP value: 20 to 40), preferably 21 to 39, more preferably 22 to 38, and still more preferably 23 to 37. By making the SP value of the non-aqueous liquid in the above range, the contact efficiency between the lithium and titanium residues contained in the polymer solution prepared in Step 1 and the non-aqueous liquid becomes appropriate, and in Step 3 described later, Since the transition to the aqueous phase is promoted, a purified polymer solution with little metal residue is finally obtained.

  The non-aqueous liquid having an SP value of 20 to 40 is not particularly limited. For example, n-butanol (SP value = 28.7), isopropyl alcohol (SP value = 23.5), ethanol (SP value = 26.2). ), Methanol (SP value = 29.7), 1-octanol (SP value = 20.9), allyl alcohol (SP value = 25.8), furfuryl alcohol (SP value = 24.3), ethylene glycol ( SP value = 34.9), glycerol (SP value = 36.2), dimethylformamide (SP value = 24.7), nitromethane (SP value = 26.0), dimethyl sulfoxide (SP value = 26.4), In addition to propylene glycol (SP value = 20.7), an amine compound such as ethylenediamine (SP value = 25.2) may be used. These non-aqueous liquids having an SP value of 20 to 40 can be used alone or in combination. Alcohol is preferable from the viewpoint of ease of handling, and isopropyl alcohol, ethanol, and methanol are more preferable.

  In step 2, the addition amount of the non-aqueous liquid is 0.0001 to 0.01 volume times, preferably 0.0002 to 0.008 volume times with respect to the polymer solution containing lithium or titanium residue, and 0.0005. -0.005 volume times is more preferable. When the addition amount of the non-aqueous liquid is within the above range, the lithium or titanium residue contained in the polymer solution is sufficiently in contact with the non-aqueous liquid, and the transition to the aqueous phase in step 3 is promoted. This is preferable because the metal residue is easily removed and the burden of waste liquid treatment is reduced.

(Mixing conditions)
In step 2, the mixing method of the polymer solution and the non-aqueous liquid is obtained as the product of the P / V value (kw / m ³ ) representing the stirring strength and the stirring time T (sec) (P / V) · T. Mixing is performed under conditions where the value is 100 or more. Here, P (kw) is the power required for stirring, and can be easily obtained by measuring the power consumption during mixing. V (m ³ ) is the spatial volume of the mixing part, and is the spatial volume of the part that gives a shearing force to the solution.

(P / V) · T value is preferably 500 or more, more preferably 1000 or more, and still more preferably 3000 or more. By setting the (P / V) · T value in the above range, a high metal removal effect can be obtained. In particular, mixing can be performed at a high P / V value of 3 × 10 ⁴ (kw / m ³ ) or more by using a rotary disperser having a meshing structure as described in JP-A-6-133604. Since a (P / V) · T value of 3000 or more can be obtained even with a short mixing time of about 0.1 sec, the metal removal treatment can be performed in a very short time, which is preferable.

[Step 3]
In the method for purifying a polymer solution of the present embodiment, in Step 3, 0.1 to 10 times volume of water is added to the mixed solution obtained in Step 2, and (P / V) · T value is 100. It is the process of mixing on the above conditions.

  In step 3, the purpose is to extract and disperse lithium and titanium residues contained in the polymer solution in the aqueous phase.

  The amount of water added in step 3 is 0.1 to 10 times by volume, preferably 0.3 to 5 times by volume, and more preferably 0.5 to 2 times by volume. If the amount of water added to the mixture obtained in step 2 is within the above range, lithium and titanium residues contained in the polymer solution can be efficiently extracted and dispersed in the aqueous phase, Since the separability of a later polymer solution phase and an aqueous phase becomes favorable, it is preferable.

(Mixing conditions)
In the method of mixing the mixed solution and water in Step 3, the mixing is performed under the condition that the (P / V) · T value is 100 or more.

(P / V) · T value is preferably 500 or more, more preferably 1000 or more, and still more preferably 3000 or more. By setting the (P / V) · T value in the above range, a high metal removal effect can be obtained. As in step 2, by using a rotary disperser having a meshing structure as described in JP-A-6-136634, a high P / V value of 3 × 10 ⁴ (kw / m ³ ) or more is obtained. Since it can be mixed and a (P / V) · T value of 3000 or more can be obtained even with a short mixing time of about 0.1 sec, it is preferable because the metal removal treatment can be performed in a very short time.

  In the purification method of the polymer solution of this embodiment, the removal of lithium and titanium residues is completed by finally separating the polymer solution phase and the aqueous phase. The method for separating the polymer solution phase from the aqueous phase is not particularly limited as long as it is generally used in the art. For example, the mixed solution composed of the polymer solution and the aqueous layer is separated and centrifuged. Examples thereof include a method of removing the aqueous phase by separation, countercurrent extraction, and the like.

  Conventionally, since the polymer solution and water have low compatibility, there is a limit in removing lithium and titanium residues in the polymer solution using water. On the other hand, the polymer solution and alcohol have good compatibility, but there are problems such as poor separation after mixing and a long time for separation. In order to overcome these problems, a method of adding water and alcohol in combination to a polymer solution is known, but it is still difficult to remove lithium and titanium residues incorporated in the polymer solution at a high level. It is.

  On the other hand, in the present embodiment, the polymer solution and a component (non-aqueous liquid) highly compatible with the polymer solution are mixed in advance so that the lithium or titanium residue and the non-aqueous liquid are sufficiently brought into contact with each other. Thereafter, the metal residue can be effectively removed into the aqueous phase by adding and mixing water as an extraction phase.

(Purified polymer solution)
Since the metal residue contained in the polymer solution efficiently migrates into the aqueous phase, the finally obtained purified polymer solution has the metal residue removed compared to the polymer solution prepared in Step 1. .

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these.

[Production Example 1]
Polystyrene-polybutadiene-polystyrene block copolymer (styrene content: 30.0% by mass, butadiene content: 70.0% by mass, number average molecular weight: 50,000) by a conventionally known anionic polymerization method using alkyl lithium as an initiator. ) In a 20 wt% cyclohexane solution (SP value = 16.8). After the polymer solution was dried to remove cyclohexane, the amount of metal contained in the polymer was analyzed by elemental analysis (ICPS-7510, manufactured by Shimadzu Corporation) using inductively coupled plasma (ICP). As a result, the amount of Li residue was 100 ppm.

[Production Example 2]
2800 g of a cyclohexane solution containing 400 g of the polystyrene-polybutadiene-polystyrene block copolymer obtained in Production Example 1 was placed in a 5-liter autoclave reactor and heated to 60 ° C. while stirring at 400 rpm. Thereafter, 1.5 mmol of triethylaluminum and 0.8 mmol of bis (cyclopentadienyl) titanium dichloride are added, and a hydrogenated polymer solution is obtained by pressurizing with 10 kg / cm ² of hydrogen to perform a hydrogenation reaction. (Cyclohexane solution, SP value = 16.8) was obtained. As a result of analyzing the hydrogenated polymer (polymer) by NMR, it was confirmed that 98% or more of the double bonds in the polybutadiene block were hydrogenated. The amount of metal contained in the obtained polymer was measured through elemental analysis using inductively coupled plasma (ICP), and as a result, Ti residue: 102 ppm, Li residue: 100 ppm, Al residue: 101 ppm. It was.

[Example 1]
After adding 0.001 volume times ethylenediamine (SP value = 25.2) to the polymer solution obtained in Production Example 1, the temperature was raised to 60 ° C. in a tank equipped with a stirring blade, and (P / V). Mixing was performed at T value = 300. Thereafter, an equal volume of water was further added to the mixed solution, and mixing was performed at (P / V) · T value = 300. The obtained mixed solution was allowed to stand and separate in a tank for 15 minutes, and the obtained polymer solution was vacuum-dried to obtain a solid polymer. The amount of metal contained in the obtained solid polymer was measured through elemental analysis using inductively coupled plasma (ICP). The measurement results are shown in Table 1.

[Example 2]
After adding 0.001 volume times ethanol (SP value = 26.2) to the polymer solution obtained in Production Example 2, the temperature was raised to 60 ° C. in a tank equipped with a stirring blade, and (P / V). Mixing was performed at T value = 300. Thereafter, an equal volume of water was further added to the mixed solution, and mixing was performed at (P / V) · T value = 300. The obtained mixed solution was allowed to stand and separate in a tank for 15 minutes, and the obtained polymer solution was vacuum-dried to obtain a solid polymer. The amount of metal contained in the obtained solid polymer was measured through elemental analysis using inductively coupled plasma (ICP). The measurement results are shown in Table 1.

[Comparative Example 1]
An equal volume of water is added to the polymer solution obtained in Production Example 2, the temperature is raised to 60 ° C. in a tank with a stirring blade, and mixing is performed at (P / V) · T value = 300. went. The obtained mixed solution was allowed to stand and separate in a tank for 15 minutes, and the obtained polymer solution was vacuum-dried to obtain a solid polymer. The amount of metal contained in the obtained solid polymer was measured through elemental analysis using inductively coupled plasma (ICP). The measurement results are shown in Table 1.

  The method for purifying a polymer solution of the present invention has industrial applicability as a method for removing a catalyst residue of a homogeneous catalyst remaining in a polymer solution.

Claims (5)

Step 1 for preparing a polymer solution containing an organic solvent having a solubility parameter of less than 20 (MPa) ^1/2 and containing at least lithium and / or titanium;
A non-aqueous liquid having a solubility parameter of 20 to 40 (MPa) ^1/2 is added by 0.0001 to 0.01 volume times with respect to the polymer solution, and the condition (P / V) · T value ≧ 100 is satisfied. Step 2 of obtaining a mixed solution by mixing;
Step 3 of adding 0.1 to 10 times volume of water to the mixture, and mixing under the condition of (P / V) · T value ≧ 100;
A method for purifying a polymer solution comprising:   The method for purifying a polymer solution according to claim 1, wherein the solubility parameter of the organic solvent is in the range of 14-18.   The method for purifying a polymer solution according to claim 1 or 2, wherein the solubility parameter of the non-aqueous liquid is in the range of 23 to 37.   The method for purifying a polymer solution according to claim 1, wherein the non-aqueous liquid is alcohol.   The method for purifying a polymer solution according to claim 1, wherein the polymer solution further contains aluminum.