WO2019159752A1

WO2019159752A1 - Waste water reutilization method

Info

Publication number: WO2019159752A1
Application number: PCT/JP2019/004003
Authority: WO
Inventors: 伊藤　修
Original assignee: 日本ゼオン株式会社
Priority date: 2018-02-14
Filing date: 2019-02-05
Publication date: 2019-08-22
Also published as: TW201942068A

Abstract

This method is for reutilization of waste water containing a metal component that is generated in a phase separation process of causing phase separation by mixing an alkaline aqueous solution with a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing the metal component, the method comprising: a precipitation step for precipitating a precipitate containing the metal component contained in the waste water by performing pH adjustment on the waste water generated by the phase separation, to obtain an aqueous dispersion in which the precipitate is dispersed; a centrifugation step for separating the precipitate by performing a centrifugal operation on the aqueous dispersion in which the precipitate is dispersed; and a reutilization step for reutilizing the separation liquid obtained by the centrifugal operation in order to prepare an alkaline aqueous solution that is to be used in the phase separation step.

Description

Wastewater recycling method

The present invention performs phase separation by mixing waste water generated in the production of a polymer, specifically, a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component and an alkaline aqueous solution. The present invention relates to a wastewater recycling method that can suitably reuse wastewater containing metal components.

Various polymers such as polybutadiene, polyisoprene, styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene-styrene block copolymer (SBS) are solution-polymerized using homogeneous catalysts containing metal components. (For example, refer to Patent Document 1).

On the other hand, when these polymer solutions obtained by solution polymerization are solidified by a phase separation step in which phase separation is performed by adding water or an aqueous solution, wastewater generated by such a phase separation step. A metal component derived from the homogeneous catalyst is contained therein. Therefore, if such wastewater is reused in a phase separation process or the like, the problem is that the metal component derived from such a homogeneous catalyst causes clogging in piping and the resulting polymer There was a problem that the content ratio of the metal component derived from the homogeneous catalyst in the inside became high, and the quality of the obtained polymer was lowered. Therefore, the current situation is that the wastewater generated by such a phase separation process is not being reused.

JP 2004-83667 A

The present invention has been made in view of such a situation, and performs phase separation by mixing a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component and an alkaline aqueous solution. It is an object of the present invention to provide a method for reusing wastewater, which can suitably reuse wastewater containing metal components that is generated when the wastewater is discharged.

As a result of diligent research to achieve the above-mentioned object, the inventors have made a phase separation by mixing a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component and an alkaline aqueous solution. For the wastewater containing metal components generated in the phase separation step, the pH adjustment is performed to precipitate precipitates containing the metal components contained in the wastewater, and the aqueous dispersion in which such precipitates are dispersed is centrifuged. As a result, it was found that such waste water can be suitably reused in the phase separation step, and the present invention has been completed.

That is, according to the present invention, the metal component produced in the phase separation step of phase separation by mixing a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component and an alkaline aqueous solution, The wastewater generated by phase separation is precipitated by dispersing the precipitate containing the metal component contained in the wastewater by adjusting the pH of the wastewater generated by phase separation. A precipitation step for obtaining an aqueous dispersion, a centrifugal step for separating the precipitate by performing a centrifugal operation on the aqueous dispersion in which the precipitate is dispersed, and a separation liquid obtained by the centrifugal operation There is provided a wastewater recycling method comprising: a reuse step for use in the phase separation step and reused for the preparation of an alkaline aqueous solution.

In the reuse method of the present invention, after the centrifugation step, the method further comprises a step of measuring the conductivity of the separation liquid obtained by the centrifugation operation, and according to the conductivity of the separation liquid, in the precipitation step It is preferable to change pH adjustment conditions and / or centrifugation conditions in the centrifugation step.
In the recycling method of the present invention, the homogeneous catalyst is preferably an organoaluminum compound.
In the recycling method of the present invention, the polymer solution is preferably a polybutadiene solution.
In the recycling method of the present invention, it is preferable that the centrifugation in the centrifugation step is performed using a decanter type centrifuge.
In the recycling method of the present invention, the alkaline aqueous solution is preferably an aqueous solution of an alkali metal hydroxide.
In the recycling method of the present invention, the pH value after pH adjustment in the precipitation step is preferably in the range of 6-8.

The wastewater containing a metal component, which is generated when phase separation is performed by mixing a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component, and an alkaline aqueous solution, is preferably reused. It is possible to provide a method for recycling wastewater.

FIG. 1 is a diagram showing an example of a reuse system to which the wastewater reuse method of the present invention is applied. FIG. 2 is a diagram showing an example of a centrifugal separator used in the wastewater recycling method of the present invention.

The method for recycling wastewater of the present invention is as follows:
A method of reusing wastewater containing a metal component generated in a phase separation step of phase separation by mixing a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component and an alkaline aqueous solution. There,
About the wastewater generated by phase separation, by performing pH adjustment, a precipitation step of obtaining an aqueous dispersion in which the precipitate is dispersed by precipitating the precipitate containing the metal component contained in the wastewater;
For the aqueous dispersion in which the precipitate is dispersed, a centrifugal separation step for separating the precipitate by performing a centrifugal separation operation;
And a reuse step of reusing the separation liquid obtained by the centrifugation operation for the preparation of the alkaline aqueous solution used in the phase separation step.

The wastewater recycling method of the present invention occurs in a phase separation step in which phase separation is performed by mixing a polymer solution obtained by performing polymerization using a homogeneous catalyst containing a metal component and an alkaline aqueous solution. This is a method of reusing wastewater containing a metal component derived from a homogeneous catalyst.

The homogeneous catalyst containing a metal component is not particularly limited as long as it is a catalyst that dissolves in a water-insoluble organic solvent, but is not limited to an organic alkali metal compound; an organic alkaline earth metal compound; an organoaluminum compound; And the like, and cyclopentadienyl titanium compounds. In the present specification, “homogeneous catalyst containing a metal component” and “homogeneous catalyst” include a catalyst residue derived from the homogeneous catalyst after polymerization, and the catalyst residue usually contains a metal component. Including.

Among these, from the viewpoint of high reuse efficiency in the wastewater reuse method of the present invention, an organoaluminum compound is preferable as the homogeneous catalyst containing a metal component.

An organoaluminum compound is a compound in which at least one hydrocarbon group is bonded to an aluminum atom. The hydrocarbon group is not particularly limited, but is preferably an alkyl group, more preferably an alkyl group having 1 to 10 carbon atoms, and particularly preferably an alkyl group having 2 to 4 carbon atoms.

Specific examples of the organoaluminum compound include organoaluminum halide compounds such as diethylaluminum monochloride, diethylaluminum monobromide, dibutylaluminum monochloride, dicyclohexylaluminum monochloride, diphenylaluminum monochloride, ethylaluminum sesquichloride, ethylaluminum dichloride. Alkylalkyl compounds such as trimethylaluminum, triethylaluminum, triisopropylaluminum, and triisobutylaluminum; organic aluminum hydride compounds such as diethylaluminum hydride and ethylaluminum sesquihydride. Among these, an organoaluminum halide compound and an alkylaluminum compound are preferable, diethylaluminum monochloride, ethylaluminum sesquichloride, ethylaluminum dichloride, and triisobutylaluminum are more preferable, and diethylaluminum monochloride is particularly preferable. These organoaluminum compounds can be used alone or in combination of two or more.

Further, when an organoaluminum compound is used as the homogeneous catalyst containing a metal component, it is preferable to use a transition metal compound in combination. As the transition metal compound, an iron group or platinum group of Groups 8 to 10 of the periodic table is used. Compounds containing group elements are preferred, cobalt compounds and nickel compounds are more preferred, and cobalt compounds are particularly preferred.

Specific examples of the transition metal compound include inorganic acid salts such as cobalt chloride, cobalt bromide and cobalt nitrate; cobalt hexanoate, cobalt 2-ethylhexanoate, cobalt stearate, cobalt naphthenate, cobalt acetate, cobalt oxalate Organic acid salts such as cobalt versatate (a cobalt salt of an aliphatic monocarboxylic acid having 6 to 20 carbon atoms having a carboxyl group on a tertiary carbon in which three alkyl groups having 1 or more carbon atoms are bonded), cobalt malonate; Organic base complexes such as cobalt bisacetylacetonate, cobalt trisacetylacetonate, ethyl acetoacetate cobalt, cobalt halide triarylphosphine complex, trialkylphosphine complex, pyridine complex and picoline complex; The corresponding nickel compounds are listed It is. These transition metal compounds may be used alone or in combination of two or more. Among these, cobalt hexanoate, cobalt 2-ethylhexanoate, cobalt stearate, cobalt naphthenate, and nickel compounds corresponding to these are preferable, and cobalt 2-ethylhexanoate is particularly preferable.

The polymer solution contains a water-insoluble organic solvent and a polymer in addition to the above homogeneous catalyst. In the polymer solution, the polymer is dissolved in the water-insoluble organic solvent. It is contained in. The polymer is not particularly limited as long as it is obtained by polymerization using a homogeneous catalyst and can be dissolved in a water-insoluble organic solvent. Specific examples of the polymer include polybutadiene, polyisoprene, styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene-styrene block copolymer (SBS), and styrene-ethylene-butadiene-styrene block copolymer. (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and the like. Among these, polybutadiene is preferred from the viewpoint that it can be suitably produced by polymerization using an organoaluminum compound.

The weight average molecular weight (Mw) of the polymer is not particularly limited, but is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent, preferably 30,000 to 300, 000, more preferably 35,000 to 250,000.

The molecular weight distribution (Mw / Mn) of the polymer is not particularly limited, but is preferably 2.0 or less, more preferably 1.5 or less, and particularly preferably 1.2 or less. The molecular weight distribution (Mw / Mn) of the polymer is the polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) using THF as a solvent. The divided value (Mw / Mn).

The water-insoluble organic solvent is not particularly limited as long as the polymer is soluble. Specific examples of the water-insoluble organic solvent include butane, pentane, hexane, heptane, cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, decahydronaphthalene, bicycloheptane, tricyclodecane, Saturated hydrocarbons such as hexahydroindenecyclohexane and cyclooctane; unsaturated hydrocarbons such as 1-butene, 2-butene, 1-pentene and 2-pentene; aromatic hydrocarbons such as benzene, toluene and xylene; nitromethane, nitrobenzene , Nitrogen-containing hydrocarbons such as acetonitrile, dimethylformamide and N-methylpyrrolidone; ethers such as diethyl ether and tetrahydrofuran; chloroform and dichloromethane Chlorobenzene, halogen-containing hydrocarbons such as dichlorobenzene; propylene glycol; and the like. Among these, unsaturated hydrocarbons, saturated hydrocarbons and aromatic hydrocarbons are preferable, and saturated hydrocarbons are more preferable. Said water-insoluble organic solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

As a polymerization reaction for obtaining a polymer solution, any of radical polymerization, anion polymerization, cation polymerization, coordination anion polymerization, coordination cation polymerization, living polymerization and the like may be used. Examples of living polymerization include living anion polymerization, living cation polymerization, and living radical polymerization. From the viewpoint of easy control of the weight average molecular weight and structure of the resulting polymer and easy polymerization operation, a polymerization reaction by living polymerization is preferable, and a polymerization reaction by living anion polymerization is more preferable.

Next, the wastewater recycling method of the present invention will be described with reference to the case of using the recycling system shown in FIG. FIG. 1 is a diagram showing an example of a reuse system to which the wastewater reuse method of the present invention is applied.
The recycling system shown in FIG. 1 includes a coagulation tank 1, a precipitation tank 2, an acid storage tank 3, and a centrifuge 4.

(Phase separation process)
In the phase separation step, a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component, such as a polymer solution obtained by a polymerization reaction, is mixed with an alkaline aqueous solution to cause phase separation. In this step, polymer crumb is precipitated.

For example, when the recycling system shown in FIG. 1 is used, a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component is continuously supplied to a coagulation tank 1 containing an alkaline aqueous solution. , Mixing causes phase separation, and polymer crumb is precipitated by coagulation. Alternatively, a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component is continuously supplied to the coagulation tank 1, and these are removed by steam stripping using an alkaline aqueous solution in the coagulation tank 1. Mixing may cause phase separation, and polymer crumb may be precipitated by coagulation. At this time, polymer crumb is precipitated and serum water containing a metal component derived from the homogeneous catalyst is generated. The recycling method of the present invention is at least one of such waste water. Part is reused in the phase separation process.

Therefore, in the phase separation step, an alkaline aqueous solution is used to cause phase separation in the polymer solution and precipitate the polymer crumb. In the present invention, as described later, Of the aqueous solution, as at least a part, serum water as waste water generated by the phase separation process is used.

The base used to form the alkaline aqueous solution is not particularly limited, and examples thereof include organic bases such as triethylamine and ethylenediamine, and alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; sodium carbonate, Examples include alkali metal carbonates such as potassium carbonate and sodium hydrogen carbonate; and inorganic bases such as ammonia. Of these, alkali metal hydroxides can be preferably used. The pH of the alkaline aqueous solution used in the phase separation step is not particularly limited, but is preferably in the range of 9.5 to 12.5. In the phase separation step, a crumbing agent may be used in combination.

(Precipitation process)
In the precipitation step, the pH of the waste water containing the metal component derived from the homogeneous catalyst (serum water) generated by the phase separation step is adjusted to adjust the precipitate containing the metal component derived from the homogeneous catalyst. This is a step of obtaining an aqueous dispersion containing such precipitates by precipitation.

For example, when the recycling system shown in FIG. 1 is used, waste water (serum water) containing a metal component derived from the homogeneous catalyst discharged from the coagulation tank 1 is continuously supplied to the precipitation tank 2. In the precipitation tank 2, the pH is adjusted by mixing with the acid component supplied from the acid storage tank 3. And in the precipitation tank 2, it can be set as the aqueous dispersion containing such a deposit by depositing the deposit containing the metal component derived from a homogeneous catalyst.

In addition, the deposit containing the metal component derived from the homogeneous catalyst is usually dispersed and contained in the aqueous dispersion in a floating state. Therefore, in the precipitation step, the precipitation of the precipitate containing the metal component derived from the homogeneous catalyst in the precipitation tank 2 and the discharge of the aqueous dispersion containing such a precipitate from the precipitation tank 2 are as follows: Can be done continuously.

The acid component used for pH adjustment is not particularly limited, and examples thereof include hydrochloric acid, nitric acid, sulfuric acid and the like, and these are preferably added in the form of an aqueous solution.

In the precipitation step, the pH value after pH adjustment when performing pH adjustment is not particularly limited, and may be appropriately selected according to the type of metal component derived from the homogeneous catalyst contained in the waste water. In the case where an organoaluminum compound is used as a homogeneous catalyst, and the metal component contained in the waste water is mainly aluminum, the pH after pH adjustment from the viewpoint of appropriately depositing precipitates containing aluminum The value is preferably in the range of 6 to 8, more preferably in the range of 6.5 to 7.5, and even more preferably in the range of 6.8 to 7.2.

1 includes an inlet pH meter 5, an outlet pH meter 6, and a flow control valve 7, as shown in the figure. The inlet pH meter 5 is installed on the upstream side of the precipitation tank 2 and can measure the pH value of waste water (serum water) supplied to the precipitation tank 2. On the other hand, the outlet pH meter 6 is installed on the downstream side with respect to the precipitation tank 2 and can measure the pH value of the aqueous dispersion containing precipitates derived from the metal components discharged from the precipitation tank 2. Further, the flow rate control valve 7 is a control valve for controlling the supply amount of the acid component from the acid storage tank 3 to the precipitation tank 2.

Then, according to the reuse system shown in FIG. 1, the measured value of the outlet pH meter 6 is compared with the target pH value after pH adjustment, and the measured value (actual pH value) of the outlet pH meter 6 is the target value. When the pH value deviates from the pH value, the flow rate control valve 7 is adjusted based on the measured value by the inlet pH meter 5 and the measured value by the outlet pH meter 6 to supply the acid component to the precipitation tank 2. The amount can be adjusted, whereby the pH can be adjusted appropriately in the precipitation step.

In addition, it is preferable that the pH value adjustment by the inlet pH meter 5, the outlet pH meter 6, and the flow rate control valve 7 is automatically performed using these measured values, and feedback. It is particularly preferable to carry out by control. In this case, it is preferable that such feedback control is performed by a control device CTR (not shown).

In feedback control, for example, the control device CTR calculates the difference ΔpH between the pH value of the outlet pH meter 6 and the target pH value after pH adjustment (ΔpH = pH value of the outlet pH meter 6−target pH value). The supply amount of the acid component to the precipitation tank 2 is automatically adjusted by controlling the flow rate control valve 7 based on the calculated difference ΔpH value and the measured value at the inlet pH meter 5. be able to.

For example, when the target pH value after pH adjustment is 7.5 and the measured value by the outlet pH meter 6 is 8, that is, when the difference ΔpH is +0.5, the flow control valve 7 is turned on. Control is performed to increase the supply amount of the acid component to the precipitation tank 2. In this case, the increase amount of the supply amount of the acid component to the precipitation tank 2 is calculated based on the measured value by the inlet pH meter 5 and the measured value by the outlet pH meter 6. Alternatively, when the target pH value after pH adjustment is 7.5 and the measured value by the outlet pH meter 6 is 7, that is, when the difference ΔpH is −0.5, the flow control valve 7 Is controlled to reduce the supply amount of the acid component to the precipitation tank 2. At this time, the decrease amount of the supply amount of the acid component to the precipitation tank 2 is also calculated based on the measured value by the inlet pH meter 5 and the measured value by the outlet pH meter 6.

It should be noted that the adjustment amount when automatically adjusting the supply amount of the acid component can be automatically calculated based on the past measurement value, and in this case, a control map set for each water temperature or A control map or correction value set for each processing amount in the precipitation process, a correction map, or a control map or correction value set for each water temperature and processing amount is stored in the control device CTR. It is good also as an aspect which controls the adjustment amount in the case of referring automatically and adjusting the supply amount of an acid component. Furthermore, these control maps and correction values may be automatically calculated by the control device CTR from past measurement values.

(Centrifugation process)
A centrifugation process is a process of isolate | separating a precipitate by performing centrifugation operation about the aqueous dispersion liquid which the precipitate disperse | distributed obtained by the said precipitation process.

For example, when the reuse system shown in FIG. 1 is used, an aqueous dispersion in which precipitates are continuously discharged from the precipitation tank 2 is continuously supplied to the centrifugal separator 4 and the centrifugal separator is provided. The aqueous dispersion in which the precipitate is dispersed is separated into the precipitate and the separation liquid (supernatant liquid) by continuously performing the centrifugal separation operation according to 4.

The centrifugal separator 4 is not particularly limited as long as it is an apparatus that can continuously perform a centrifugal operation. However, the precipitate can be more appropriately separated from the aqueous dispersion in which the precipitate is dispersed. It is preferable to use a decanter type centrifuge from the point that it can be performed. As the decanter-type centrifuge, for example, a decanter-type centrifuge having a screw conveyor, which is provided in an outer rotary cylinder and is relatively rotatable within the outer rotary cylinder, as shown in FIG. 2, is preferably used. it can.

The decanter type centrifuge shown in FIG. 2 includes an outer rotating cylinder 41 that can rotate in the direction of the arrow in FIG. 2, and a screw that is coaxial with the outer rotating cylinder 41 and that can rotate with a slight rotational difference. A conveyor 42, a feed tube 43 for supplying an aqueous dispersion in which precipitates are dispersed, a solid material discharge port 44, and a dam plate 45 for adjusting the liquid level are provided. In FIG. 2, reference numeral 46 denotes a drive motor, and reference numeral 47 denotes a gear box. By the action of the drive motor 46 and the gear box 47, the outer rotary cylinder 41 and the screw conveyor 42 are arbitrarily arranged in the direction of the arrow in FIG. 2. It can rotate at speed. The screw conveyor 42 includes screw blades 48 formed in a spiral shape.

Then, the centrifugal operation in the case of using the decanter type centrifugal separator shown in FIG. 2 will be described. First, an aqueous dispersion in which precipitates are dispersed is supplied through a feed tube 43 provided in the screw conveyor 42. Through the mouth 49, the outer rotating cylinder 41 is continuously supplied into the outer rotating cylinder 41 that rotates at a high speed, and a high centrifugal force is applied to the aqueous dispersion by the rotation of the outer rotating cylinder 41. The precipitate is separated by settling. Then, the sediment separated and settled is scraped by the screw blades 48 of the screw conveyor 42 that is coaxial with the outer rotary cylinder 41 and rotates with a slight rotational difference, and sequentially reaches the solid discharge port 44. In the direction, the solid material is continuously discharged from the solid material outlet 44 to the outside of the decanter centrifuge. On the other hand, the separation liquid obtained by removing the precipitate overflows and is discharged from a dam plate 45 provided on the side opposite to the solid discharge port 44 for adjusting the liquid level.

In the decanter-type centrifuge shown in FIG. 2, the centrifugal force in the centrifugal operation is generated by the rotation of the outer rotating cylinder 41, so that the centrifugal force is adjusted according to the rotational speed of the outer rotating cylinder 41. Can do. Therefore, when the decanter-type centrifuge shown in FIG. 2 is used, the centrifugal force in the centrifugal operation may be set within the above range by adjusting the rotational speed of the outer rotating cylinder 41. The following formula (1) is established between the rotational speed of the outer rotating cylinder 41 and the centrifugal force.
^{RCF = R × N 2/874} (1)
(In the above formula (1), RCF is the centrifugal force (unit: G), R is the radius of rotation of the outer rotating cylinder 1 (unit: m), and N is the number of rotations per minute (unit: rpm).)

In addition, when the decanter centrifuge shown in FIG. 2 is used, the supply speed of the aqueous dispersion in which the precipitate is dispersed to the decanter centrifuge is, for example, the water dispersion in which the precipitate is dispersed in the feed tube 43. What is necessary is just to adjust to the said range by controlling the liquid feeding pressure of the pump for sending a liquid.

The difference in rotational speed between the outer rotating cylinder 41 and the screw conveyor 42 may be set as appropriate, but is preferably 15 rotations or less per minute, and more preferably 12 rotations or less. By setting the difference between the rotational speeds of the outer rotating cylinder 41 and the screw conveyor 42 within such a range, it is possible to more appropriately remove the precipitate from the aqueous dispersion in which the precipitate is dispersed. Further, the temperature at the time of the centrifugation treatment is preferably 30 to 100 ° C., more preferably 70 to 90 ° C.

(Reuse process)
The reuse step is a step of reusing the separation liquid obtained by the centrifugation operation in the centrifugation step for the preparation of the alkaline aqueous solution used in the above-described phase separation step.

For example, when the reuse system shown in FIG. 1 is used, a phase separation step is performed after adding a base as necessary to the separation liquid separated from the precipitate continuously discharged from the centrifugal separator 4. It is reused in the phase separation process by returning to the coagulation tank 1 used for the above. In addition, when the water-insoluble organic solvent component is contained in the separated liquid from which the precipitate is separated, the water-insoluble organic solvent component is removed by a known method such as a distillation method and then returned to the coagulation tank 1. It is good also as an aspect.

According to the recycling method of the present invention, it is derived from the homogeneous catalyst from the waste water containing the metal component derived from the homogeneous catalyst, which is generated by the phase separation process, through the precipitation step and the centrifugal separation step described above. A metal component can be appropriately removed. Therefore, even when such wastewater is reused in the phase separation process, the problem of clogging in piping and the like, and the content ratio of the metal component derived from the homogeneous catalyst in the obtained polymer are It is possible to effectively solve the problem that the quality of the obtained polymer is lowered due to the increase. As a result, the waste water containing the metal component derived from the homogeneous catalyst generated by the phase separation step can be effectively reused, thereby improving the productivity.

In addition, the reuse system shown in FIG. 1 includes an electric conductivity meter 8 on the downstream side of the centrifugal separator 4, and the precipitate is separated by the electric conductivity meter 8 and used for reuse. The electrical conductivity of can be measured.

According to the reuse system shown in FIG. 1, by measuring the conductivity of the separated liquid to be reused by the conductivity meter 8, the measured conductivity is used to separate the separated liquid to be reused. The residual amount of the metal component derived from the homogeneous catalyst can be measured. In the recycling system shown in FIG. 1, the pH adjustment conditions in the precipitation step and / or the centrifugation conditions in the centrifugation step are automatically changed according to the measured residual amount of the metal component derived from the homogeneous catalyst. To control.

For example, when the conductivity measured by the conductivity meter 8 becomes higher than a predetermined specified value (the residual amount of the metal component derived from the homogeneous catalyst, which is obtained from the conductivity meter 8, is less than the predetermined specified value). In the case of using a decanter type centrifuge as shown in FIG. 2, the outer rotating cylinder 41 is used for the centrifuge 4 via the control device CTR described above. The number of rotations) can be automatically controlled. In this case, the increase in the number of rotations of the centrifugation is set according to the value of the conductivity measured by the conductivity meter 8.

Alternatively, as another control mode when the conductivity measured by the conductivity meter 8 is higher than a predetermined specified value, the target pH value after pH adjustment in the above-described precipitation step is performed by the control device CTR described above. Further, it is possible to adopt a mode in which control for resetting to a lower value is performed, and such control can be performed in combination with the above-described increase control of the rotation speed of the centrifuge in the centrifuge 4. When the target pH value after pH adjustment in the precipitation process is reset to a lower value by the controller CTR, the difference ΔpH (ΔpH = ΔpH) between the measured value by the outlet pH meter 6 and the target pH value. Since the pH value of the outlet pH meter 6 minus the target pH value is normally a positive value, control for increasing the supply amount of the acid component to the precipitation tank 2 is performed by automatic control such as the feedback control described above. Is called.

Further, for example, when the conductivity measured by the conductivity meter 8 is higher than the predetermined specified value by a value equal to or less than the first predetermined value, the rotation of the centrifuge in the centrifuge 4 described above. Only the control for increasing the number is performed, and the conductivity measured by the conductivity meter 8 is larger than the first predetermined value with respect to the predetermined specified value, and the second predetermined value (second When the predetermined value> the first predetermined value) is increased, it is preferable that the control for resetting the target pH value after the pH adjustment described above is performed. Furthermore, when the conductivity measured by the conductivity meter 8 is higher than the second predetermined value with respect to the predetermined specified value, the rotational speed of the centrifugal separation in the centrifugal separator 4 described above is set. You may perform both the control to increase, and the control which resets the target pH value after pH adjustment mentioned above. In this case, the value of the target pH value after resetting may be determined when resetting the target pH value after pH adjustment according to the value of the conductivity measured by the conductivity meter 8, For example, the higher the conductivity value measured by the conductivity meter 8, the lower the target pH value after resetting.

In addition, the conductivity measured by the conductivity meter 8 after the control for increasing the rotation speed of the centrifugal separation in the centrifugal separator 4 described above and the control for resetting the target pH value after the pH adjustment described above are performed. When it becomes less than the specified value, the control to reduce the rotational speed of the centrifugation step by step and the control to reset the target pH value after pH adjustment to a high value step by step automatically It is desirable to make it the aspect which performs. Further, when the control for increasing the rotation speed of the centrifugal separation in the centrifugal separator 4 described above and the control for resetting the target pH value after the pH adjustment described above are performed, for some reason, the homogeneous catalyst is used. Since the removal efficiency of the derived metal component may be lowered, it may be configured to notify an administrator or the like by issuing an alarm to that effect.

In the reuse method of the present invention, the metal component derived from the homogeneous catalyst is removed from the waste water containing the metal component derived from the homogeneous catalyst by performing automatic control based on such conductivity measurement. It can be performed more stably, and thus, such wastewater can be reused more appropriately. More specifically, even when such wastewater is reused in the phase separation process, problems such as clogging in piping and the like, and metal components derived from homogeneous catalysts in the obtained polymer Such a wastewater can be effectively reused while preventing the problem that the content ratio of the polymer becomes high and the quality of the resulting polymer is deteriorated more appropriately and stably. It is. In particular, by performing such automatic control based on the conductivity measurement, even when the removal efficiency of the metal component derived from the homogeneous catalyst is lowered for some reason, it is possible to appropriately cope with it.

As mentioned above, although the reuse method of this invention was demonstrated in detail, the reuse method of this invention is limited to the aspect which uses the reuse system shown in FIG. 1, and the aspect which uses the centrifuge apparatus shown in FIG. It is not a thing.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples.

<Example 1>
By mixing aluminum chloride and an aqueous sodium hydroxide solution, an aqueous aluminum hydroxide solution having an Al (OH) ₃ concentration of 18,000 ppm by weight and pH = 10.7 was prepared.
In addition, the aluminum hydroxide aqueous solution prepared above was prepared as what corresponds to the waste_water | drain (serum water) demonstrated below. That is, the aqueous aluminum hydroxide solution prepared above is phase-separated by mixing an aqueous sodium hydroxide solution as an alkaline aqueous solution with a polybutadiene polymer solution containing an organoaluminum compound as a homogeneous catalyst containing a metal component. It was prepared as one corresponding to the waste water (serum water) obtained at the time.

Next, the aqueous solution of aluminum hydroxide prepared above was adjusted to pH = 7.0 by adding a predetermined amount of aqueous hydrochloric acid solution, and precipitates derived from aluminum hydroxide were precipitated in the aqueous solution. An aqueous dispersion in which precipitates derived from aluminum hydroxide were suspended was obtained. When the concentration of the precipitate in the aqueous dispersion was measured, it was 18,000 ppm by weight.

Next, the aqueous dispersion in which the precipitate derived from aluminum hydroxide was suspended was subjected to a centrifugal separation operation for 180 seconds at a temperature of 80 ° C., a centrifugal force of 1,500 G, and a volume of 50 ml. As a result, a centrifuge liquid having a supernatant liquid (separate liquid) volume of 33 ml and a precipitate volume of 17 ml was obtained. And about the obtained centrifuge liquid, when the density | concentration of the deposit in a supernatant liquid (separated liquid) was measured, it is 210 weight ppm, and the density | concentration of the deposit in a deposit is 9.3 weight%. The collection rate of the precipitates by centrifugation was 98% or more. In addition, in a present Example, the density | concentration of the precipitate in each liquid is the weight before removing the water of each liquid, and the weight of the precipitate after removing water by heating at 100 degreeC for 5 minutes. I asked for it. And when the obtained supernatant liquid (separated liquid) was continuously added during the solidification process of the polybutadiene polymer solution containing the organoaluminum compound as a homogeneous catalyst containing a metal component, clogging of piping, An increase in the aluminum concentration in the polymer was not observed.

From the result of Example 1, it is obtained when the polybutadiene polymer solution containing the organoaluminum compound as a homogeneous catalyst containing a metal component is phase-separated by mixing an aqueous sodium hydroxide solution as an alkaline aqueous solution. By applying the recycling method of the present invention to waste water (serum water), a supernatant liquid (separated liquid) in which the content of aluminum, which is a metal component resulting from a homogeneous catalyst, is kept low is suitably obtained. It can be said that it is possible. Therefore, according to the recycling method of the present invention, even when such waste water (serum water) is reused in the phase separation process, problems such as clogging in piping and the like, and in the obtained polymer The wastewater (serum water) is preferably reused while effectively preventing the problem that the content ratio of the metal component derived from the homogeneous catalyst in this is high and the quality of the resulting polymer is reduced. Can be said.

<Comparative Example 1>
In the same manner as in Example 1, an aqueous dispersion having a precipitate concentration of 18,000 ppm by weight was prepared by preparing an aqueous aluminum hydroxide solution and adjusting the pH to 7.0. When the polybutadiene polymer solution containing the organoaluminum compound as a homogeneous catalyst containing a metal component is continuously fed during the solidification process, the piping is clogged. As a result, the aluminum concentration inside increased.

DESCRIPTION OF SYMBOLS 1 ... Coagulation tank 2 ... Deposition tank 3 ... Acid storage tank 4 ... Centrifugal separator 5 ... Inlet pH meter 6 ... Outlet pH meter 7 ... Flow control valve 8 ... Conductivity meter

Claims

This is a method for recycling wastewater containing a metal component, which occurs in a phase separation step in which a polymer solution obtained by a polymerization reaction using a homogeneous catalyst containing a metal component is mixed with an alkaline aqueous solution. And
About the wastewater generated by phase separation, by performing pH adjustment, a precipitation step of obtaining an aqueous dispersion in which the precipitate is dispersed by precipitating the precipitate containing the metal component contained in the wastewater;
For the aqueous dispersion in which the precipitate is dispersed, a centrifugal separation step for separating the precipitate by performing a centrifugal separation operation;
A wastewater recycling method comprising: a separation step of reusing a separation liquid obtained by the centrifugation operation for the preparation of an alkaline aqueous solution, which is used in the phase separation step.
After the centrifugation step, further comprising the step of measuring the conductivity of the separation liquid obtained by the centrifugation operation,
The method for reusing wastewater according to claim 1, wherein the pH adjustment conditions in the precipitation step and / or the centrifugation conditions in the centrifugation step are changed according to the conductivity of the separation liquid.
The method for recycling wastewater according to claim 1 or 2, wherein the homogeneous catalyst is an organoaluminum compound.
The method for recycling wastewater according to claim 3, wherein the polymer solution is a polybutadiene solution.
The method for recycling wastewater according to any one of claims 1 to 4, wherein the centrifugal separation in the centrifugal separation step is performed using a decanter type centrifugal separator.
The method for recycling wastewater according to any one of claims 1 to 5, wherein the alkaline aqueous solution is an aqueous solution of an alkali metal hydroxide.
The method for recycling wastewater according to any one of claims 1 to 6, wherein the pH value after pH adjustment in the precipitation step is in the range of 6 to 8.