JP6030850B2 - Purification method of polymer solution - Google Patents

Description

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

  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 is widely used as an elastomer.

  Such a block copolymer of a conjugated diene monomer and a vinyl aromatic monomer is a thermoplastic elastomer that is not vulcanized, and is used as an impact-resistant transparent resin or a modifier for polyolefin and polystyrene resins. However, polymers containing olefinically unsaturated double bonds can cause stability problems such as heat resistance, oxidation resistance and weather resistance due to the reactivity of the double bonds. Therefore, it is used within a limited range that is not exposed to sunlight or high temperatures. Therefore, in order to improve the durability and oxidation resistance of the polymer, hydrogen is added to the double bond in the polymer to partially or completely saturate the polymer.

  In general, various methods for hydrogenating a polymer having an olefinic double bond have been reported and can be roughly divided into the following two methods. The first method uses a heterogeneous catalyst such as a metal-supported catalyst in which a noble metal catalyst such as platinum, palladium, or rhodium is supported on carbon, silica, alumina, or the like. The second method is a method using a Ziegler catalyst using nickel or cobalt or a homogeneous catalyst of an organometallic compound such as rhodium or titanium.

  A hydrogenation reaction using a heterogeneous catalyst has a disadvantage in that a hydrogenation reaction is performed under high temperature and high pressure conditions, and after the reaction, an expensive catalyst must be recovered and reused using a filter. In addition, there is a disadvantage that the equipment cost is expensive to provide the reaction equipment. On the other hand, when a homogeneous catalyst is used, since the catalytic activity is high, there is an advantage that a high yielding hydrogenation reaction can be expected in a small amount even under mild conditions such as low temperature and low pressure. It also has the advantage of low equipment costs. However, there is a disadvantage that it is difficult to separate the homogeneous catalyst from the product after the reaction.

  Many methods of hydrogenation reaction using a homogeneous catalyst are already known. For example, a catalyst in which a group VIII metal of the periodic table, particularly a combination of a nickel or cobalt compound and an appropriate reducing agent such as an alkylaluminum compound is used. A hydrogenation method using is known.

  A hydrogenation reaction using a homogeneous catalyst generally shows a high hydrogenation rate and high reproducibility even in a small amount, but it is difficult to remove catalyst residues remaining in the polymer solution after the hydrogenation reaction. The metal component remaining in the polymer solution reacts with air or ultraviolet rays to cause degradation of the polymer or deterioration of the hue of the final polymer, which causes a reduction in commercial value, so it is desirable to remove it. In general, a homogeneous catalyst is difficult to physically separate by filtration after the reaction, and must be separated by a chemical reaction.

  Thus, several proposals have been made as methods for removing the metal residue of the homogeneous catalyst remaining in the polymer solution. For example, regarding the removal of the periodic table Group VIII metal catalyst including nickel, Patent Document 1 discloses a method of treating with an oxidizing agent and a dicarboxylic acid in order to remove the residue. Patent Document 2 discloses a method of removing a catalyst by adsorbing an oxidized metal to a silicate. Furthermore, Patent Document 3 discloses a method for removing a nickel catalyst that has reacted with oxygen by adsorbing it on activated carbon. Furthermore, Patent Document 4 discloses a method of removing a nickel catalyst using aluminum phosphate.

  As represented by these Patent Documents 1 to 4, in most cases, as a method for removing a metal element of Group VIII of the periodic table contained in the polymer solution, some additive (oxidant, organic acid, inorganic acid) , Adsorbent, etc.) need to be added.

US Pat. No. 4,595,749 US Pat. No. 5,104,972 US Pat. No. 5,089,541 US Pat. No. 3,531,448

  However, these additives may cause deterioration of the quality of the polymer if it finally remains in the polymer solution. Therefore, the addition of an additive for the purpose of removing the metal is not preferable. When such an additive is added, it is necessary to take measures such as sufficiently removing and detoxifying in the downstream process.

  This invention is made | formed in view of the problem of the prior art mentioned above, and is derived from a metal and an additive by giving a physical process with respect to the polymer solution containing the metal element of a periodic table VIII group. It is an object of the present invention to provide a method for purifying a polymer solution, which is capable of obtaining a polymer solution having a good quality with little residue.

As a result of intensive studies to solve the above problems, the present inventors physically stirred a polymer solution containing a metal element of Group VIII of the periodic table such as a nickel residue with high stirring strength. It has been found that metal residues such as solid metal particles are easily removed, and the present invention has been completed.
That is, the present invention is as follows.

[1]
Step 1 of stirring a polymer solution containing a metal element of Group VIII of the periodic table and an aqueous citric acid solution at a stirring strength (P / V value) of 100 to 1,000,000 (kW / m ³ ); ,
Step 2 of removing the solid metal residue from the stirred polymer solution by centrifugation;
A method for purifying a polymer solution comprising:

  According to the present invention, in the method of removing a metal residue remaining in a polymer solution, the polymer solution is stirred at a high stirring strength, whereby the metal residue such as solid metal particles is efficiently removed in a downstream process. Can be removed.

  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]
In the method for purifying a polymer solution of the present embodiment, a polymer solution containing a metal element of Group VIII of the periodic table is stirred at a stirring strength (P / V value) of 100 to 1,000,000 (kW / m ³ ). Step 1 to perform,
And a step 2 of removing a solid metal residue from the polymer solution after stirring.

[Step 1]
In the method for purifying a polymer solution according to the present embodiment, in Step 1, the stirring strength (P / V value) of the polymer solution containing a metal element of Group VIII of the periodic table is 100 to 1,000,000 (kW / m). ^This is the step of stirring in ³ ).

(Stirring method)
In this embodiment, in Step 1, in order to give the energy sufficient to break the interaction between the polymer and the metal residue contained in the polymer solution, and to facilitate the removal of the metal residue in Step 2, P / It is necessary to stir at a V value of 100 to 1,000,000 (kW / m ³ ). 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.

Usually, when the metal residue contained in the polymer solution is dissolved and extracted in the aqueous phase or alcohol phase by the action of an acid compound or the like, the metal residue is obtained by mixing at such high stirring strength. The contact efficiency between the acid compound and the extracted phase is increased, and the metal removal rate is improved. On the other hand, when removing the metal residue in a solid state, the metal residue is refined and dispersed in the polymer solution by performing strong stirring, and it is difficult to remove the metal residue in the downstream process. It is easily guessed. However, in this embodiment, the removal of the solid metal residue is promoted in step 2 by stirring the polymer solution with a specific stirring strength. Such specific stirring intensity P / V value is 100~1,000,000 (kW / m ^3), preferably ^{1,000~500,000 (kW / m 3),} 5,000~300 1,000 (kW / m ³ ) is more preferable. When the P / V value is smaller than the above range, the interaction between the polymer solution and the metal residue is still large, and the metal residue cannot be sufficiently removed in Step 2. On the other hand, if the P / V value is larger than the above range, the metal residue is refined by vigorous stirring and further finely dispersed in the polymer solution, so that the metal residue cannot be sufficiently removed in step 2.

  The stirring method is not particularly limited as long as the stirring strength is in the above range. For example, a method of applying a shearing force with a stirrer, a homogenizer including an emulsifier, a pump, a ball mill or a rod mill, or a high pressure A method of applying a collision force or friction force with a pulverizing roll or the like can be mentioned.

Among them, by using a rotary disperser having a meshing structure as described in JP-A-6-133604, a P / V value of 1,000 to 1,000,000 (kW / m ³ ). Stirring in the range is possible. In particular, it is preferable to perform stirring at a stirring intensity of 3 × 10 ⁴ (kW / m ³ ) or more, more preferably at least 10 × 10 ⁴ (kW / m ³ ) using a rotary disperser, It is more preferable to perform stirring of 50 × 10 ⁴ (kW / m ³ ) or more. By selecting such a stirring method having a high stirring strength, a sufficient metal removal effect can be obtained even in a short time, which is preferable from the viewpoint of productivity.

In addition, it is also possible to stir in the range of P / V value 100-10,000 (kW / m < ³ >) using a tank with a stirring blade. Such a tank with a stirring blade is not particularly limited as long as it is normally used.

(Polymer solution containing a metal element of Group VIII of the periodic table)
The polymer solution purified in the present embodiment contains a metal element of Group VIII of the periodic table. The periodic table Group VIII metal elements correspond to Group 8 to Group 10 elements of the long periodic table in the IUPAC format.

  This embodiment is very effective for removing the metal elements of Group VIII of the periodic table contained in the polymer solution. The polymer solution to be purified is not particularly limited as long as it is a polymer solution containing a metal element of Group VIII of the periodic table as a metal residue. The type of polymer in the polymer solution is not particularly limited, and may be a polymer before hydrogenation or a polymer after hydrogenation. Among these, this embodiment is suitable as a method for removing nickel residues from a solution obtained by hydrogenating a copolymer having vinyl aromatic monomer units and conjugated diene monomer units as constituent units. ing. The polymer after hydrogenation containing a nickel residue can be produced, for example, by the method described in Patent Documents 1 to 4.

  Although the number average molecular weight of the polymer contained in the polymer solution is not particularly limited, specifically, 500 to 1,000,000 is preferable, 1,000 to 850,000 is more preferable, and 5,000 to 700 is preferable. Is more preferred. Moreover, the density | concentration of a polymer solution is although it does not specifically limit, It is preferable that it is 5-50 mass%, It is more preferable that it is 7-40 mass%, It is further more preferable that it is 10-30 mass%. When the number average molecular weight of the polymer and the concentration of the polymer solution are within the above ranges, productivity is improved and the increase in viscosity is suppressed, so that the metal removal efficiency is improved. In addition, a number average molecular weight can be calculated | required by polystyrene conversion using a gel permeation chromatography (GPC).

(Stirring aid)
As described above, in step 1 of the present embodiment, the stirring aid is used only by imparting the stirring strength of P / V value of 100 to 1,000,000 (kW / m ³ ) to the polymer solution. Even if not, there is an effect of promoting the removal of a sufficient metal residue. However, a stirring aid may be added as necessary. Although it does not specifically limit as a stirring aid, When making it coexist when stirring a polymer solution by P / V value of 100-1,000,000 (kW / m < ³ >), the solid-state metal in process 2 is carried out. It is preferable to further promote the removal of the residue. Examples of such a stirring aid include acidic compounds such as organic acids or inorganic acids, coordination compounds, flocculants, and adsorbents.

  The acidic compound is not particularly limited, and specifically, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, hydrofluoric acid; carboxylic acid compound derivatives, sulfonic acid compound derivatives, hydroxy compound derivatives, Examples include organic acids such as thiol compound derivatives and enol compound derivatives, and these may be added in the form of an aqueous solution.

  Although it does not specifically limit as a coordinating compound, The thing which can be coordinated to the metal element of Group VIII of a periodic table is preferable, Specifically, a pyridine, a triphenylphosphine, ethylenediamine, bipyridine, phenanthroline, BINAP, catecholate, terpyridine , Ethylenediaminetetraacetic acid, porphyrin, cyclam, crown ethers and the like.

  The flocculant is not particularly limited, and specifically, inorganic flocculants such as polyaluminum chloride (PAC), sulfuric acid band, polyiron sulfate, polysilica iron, magnesium chloride, zeolite; polyacrylic acid type, polymethacrylic acid Examples thereof include polymer flocculants made of organic polymers such as polyamines and polyamines and having anionic, cationic, nonionic, and amphoteric ionic properties.

  The adsorbent is not particularly limited, and specific examples thereof include silica gel, activated alumina, molecular sieve, zeolite, and a polymeric synthetic adsorbent.

  The stirring aid that can be used in the present embodiment is not limited to the above-described ones, and by adding it, the interaction between the polymer and the metal residue can be interrupted, or the stirring aid and the metal residue can be more firmly connected to each other. What has the effect that it becomes easy to remove a metal residue from a polymer solution by acting is preferable. In the present embodiment, these stirring aids can be added alone or in combination of several kinds.

  The addition amount of the above-mentioned stirring aid varies depending on various factors such as the amount of metal residue in the polymer solution, the viscosity of the polymer solution, and the temperature during stirring. Therefore, it is preferable to adjust according to the state of a polymer solution and an implementation environment. For example, when an acidic compound is used as a stirring aid, the addition amount is preferably within a range in which dissolution of metal residue components does not occur.

Moreover, it is preferable to use the said stirring auxiliary agent as needed, and to keep the addition amount to the minimum necessary addition. As a result, it is possible to prevent deterioration in quality due to the stirring aid remaining in the polymer solution. In step 1 of the present embodiment, an effect of accelerating the removal of a sufficient metal residue can be obtained only by giving a stirring strength of P / V value 100 to 1,000,000 (kW / m ³ ) to the polymer solution. It is done. Therefore, it is preferable that the minimum required amount of the stirring aid is appropriately determined in accordance with the degree of removal of the target metal residue.

(Incompatible liquid)
In step 1 of the present embodiment, the stirring may be performed in a state where a liquid incompatible with the polymer solution is further added as necessary.

  The type of the incompatible liquid is not particularly limited, but when the polymer solution is a general hydrocarbon solvent system such as hexane or cyclohexane, alcohols such as water, methanol, ethanol, propanol, isopropanol; Examples include polyhydric alcohols such as ethylene glycol and polyethylene glycol. These can be used alone or in combination of two or more.

By stirring the polymer solution with a stirring strength of P / V value of 100 to 1,000,000 (kW / m ³ ) in the presence of the incompatible liquid phase such as water or alcohol, the polymer solution The metal residue therein can be efficiently dispersed in the incompatible liquid phase, and the removal effect of the metal residue can be enhanced. Usually, since the polymer solution phase has a high viscosity, it is difficult to remove metal residues from the polymer solution. However, by allowing the incompatible liquid phase to coexist as described above, the metal residue discharged from the polymer solution by vigorous stirring can be stored in the incompatible liquid phase. In addition, the metal residue once transferred to the incompatible liquid phase side does not easily re-transfer to the polymer solution phase even if stirring is continued. Therefore, the effect of removing the metal residue is further enhanced.

The addition amount of the incompatible liquid is not particularly limited, but the metal removal effect is enhanced as the addition amount increases. On the other hand, the smaller the added amount, the smaller the final drainage amount, which is preferable as a process. In this embodiment, the effect of accelerating the removal of a sufficient metal residue can be obtained only by stirring the polymer solution with a stirring intensity of P / V value of 100 to 1,000,000 (kW / m ³ ). For this reason, it is preferable to appropriately determine the addition amount according to the degree of removal of the target metal residue and the process cost.

[Step 2]
In the method for purifying a polymer solution of the present embodiment, step 2 is a step of removing a solid metal residue from the polymer solution stirred in step 1.

(Solid metal residue)
In the present embodiment, the metal residue is separated from the polymer solution after stirring by stirring the polymer solution in Step 1 with a stirring strength of P / V value of 100 to 1,000,000 (kW / m ³ ). It becomes easy to be done.

(Removal method)
The method for removing the solid metal residue from the polymer solution is not particularly limited, and it can be easily separated by a physical separation method generally used in this field. For example, methods such as centrifugation, filtration, and sedimentation can be mentioned. Among these, from the viewpoint of metal residue removal efficiency and productivity, it is preferable to remove the solid metal residue by centrifugation. The centrifuge that can be used is not particularly limited, but a disk-type centrifuge provided by Alfa Laval is preferable from the viewpoint of metal removal efficiency.

  In the present embodiment, as described above, a method in which a stirring aid and an incompatible liquid are allowed to coexist at the time of stirring in Step 1 is included. When a solid material (for example, a flocculant or an adsorbent) is used as the stirring aid, the stirring aid can be removed together with the metal residue in Step 2. On the other hand, when a liquid stirring aid is used or an incompatible liquid is added, it is preferable to remove these in Step 2 or further downstream. In particular, in Step 2, when a centrifuge is used as a method for removing solid metal residues, excess liquid components such as liquid stirring aids and incompatible liquids are removed together with solid metal residues. This is preferable from the viewpoint of productivity.

(Polymer solution after purification)
As described above, the polymer solution purification method of the present embodiment can provide a polymer solution with good quality with few metal residues and few additive residues. Moreover, the addition amount of various additives intended to improve the removal rate of metal residues can be reduced to zero or greatly reduced.

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

[Production example]
2800 g of a cyclohexane solution containing 400 g of a polystyrene-polybutadiene-polystyrene block copolymer (styrene content 30.0%, butadiene content 70.0%, number average molecular weight 50.000) obtained by anionic polymerization is placed in a 5 L autoclave reactor. Heated to 70 ° C. at 400 rpm. Thereafter, 2-ethyl-nickel hexanoic acid / triethylaluminum catalyst was added to the polymer solution so that the nickel component was 100 ppm, and hydrogenation reaction was carried out at a hydrogen pressure of 700 psig for 60 minutes, and then the temperature of the solution was raised to 90 ° C. The mixture was further held for 25 minutes to perform a hydrogenation reaction to obtain a polymer solution. As a result of analyzing the hydrogenated polymer by NMR, hydrogenation of 98% or more of double bonds in the polybutadiene block was confirmed.

[Example 1]
The polymer solution obtained in the production example was heated to 60 ° C. in a tank with a stirring blade, and stirred vigorously for 30 minutes at a stirring strength P / V value of 100 (kW / m ³ ). By filtering the solution, the solid metal residue was removed to obtain a polymer solution. After the polymer solution is vacuum dried to obtain a solid polymer, the amount of metal contained in the obtained solid polymer is determined by elemental analysis using inductively coupled plasma (ICP). Was measured with ICPS-7510 (manufactured by Shimadzu Corporation) (hereinafter the same). The measurement results are shown in Table 1.

[Example 2]
The polymer solution obtained in the production example was stirred at a stirring strength P / V value of 1.0 × 10 ⁶ (kW / m ³ ) using a rotary disperser having a meshing structure (Cabitron 1010 manufactured by Nikko Kogyo Co., Ltd.). The mixture was stirred at 60 ° C. and 7600 rpm for 1 second. Thereafter, solid metal residues were removed from the obtained polymer solution by a disk-type centrifuge (LAPX 404 manufactured by Alfa Laval, relative centrifugal acceleration 3000 G, flow rate 2.0 T / hr). The obtained polymer solution was vacuum-dried to obtain a solid polymer, and then the amount of metal contained in the obtained solid polymer was determined using inductively coupled plasma (ICP). Measured through elemental analysis. The measurement results are shown in Table 1.

Example 3
The polymer solution obtained in the production example was heated to 60 ° C. in a tank equipped with a stirring blade, and a 1% aqueous solution containing 2 moles of citric acid relative to the Ni residue was added. The mixture was vigorously stirred for 30 minutes at a V value of 100 (kW / m ³ ). Thereafter, solid metal residues were removed from the obtained polymer solution by a disk-type centrifuge (LAPX 404 manufactured by Alfa Laval, relative centrifugal acceleration 3000 G, flow rate 2.0 T / hr). The obtained polymer solution was vacuum-dried to obtain a solid polymer, and then the amount of metal contained in the obtained solid polymer was determined using inductively coupled plasma (ICP). Measured through elemental analysis. The measurement results are shown in Table 1.

[Comparative Example 1]
The polymer solution obtained in the production example was directly processed by a disk-type centrifuge (LAPX 404 manufactured by Alfa Laval, relative centrifugal acceleration 3000 G, flow rate 2.0 T / hr) without stirring. After the polymer solution is vacuum dried to obtain a solid polymer, the amount of metal contained in the obtained solid polymer is determined by elemental analysis using inductively coupled plasma (ICP). It was measured. The measurement results are shown in Table 1.

[Comparative Example 2]
The polymer solution obtained in the production example was stirred at a stirring strength P / V value of 1.5 × 10 ⁶ (kW / m ³ ) using a rotary disperser having a meshing structure (Cabitron 1010 manufactured by Nikko Kogyo Co., Ltd.). And stirring at 60 ° C. and 7600 rpm for 0.1 second. Thereafter, the obtained polymer solution was treated with a disk-type centrifuge (LAPX 404 manufactured by Alfa Laval, relative centrifugal acceleration 3000 G, flow rate 2.0 T / hr). The obtained polymer solution was vacuum-dried to obtain a solid polymer, and then the amount of metal contained in the obtained solid polymer was determined using inductively coupled plasma (ICP). Measured through elemental analysis. 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 catalyst residues remaining in the polymer solution.

Claims (1)

Step 1 of stirring a polymer solution containing a metal element of Group VIII of the periodic table and an aqueous citric acid solution at a stirring strength (P / V value) of 100 to 1,000,000 (kW / m ³ ); ,
Step 2 of removing the solid metal residue from the stirred polymer solution by centrifugation ;
A method for purifying a polymer solution comprising: